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BD-Acm Ml MISD UM78-9 USER MANUAL BAYESIA INTERACTIVE GRAPHICS RELIABILITY BY Irving E. Tamvitz John G. Mardo ASSESSMENT PROCEDURE Management Information Systems Directorate US Army Armament Research b Oevelopment Command Dover. New Jersey
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BD-Acm Ml MISD UM78-9

USER MANUAL

BAYESIA

INTERACTIVE

GRAPHICS

RELIABILITY

BY

Irving E. Tamvitz

John G. Mardo

ASSESSMENT

PROCEDURE

Management Information Systems Directorate US Army Armament Research b Oevelopment Command

Dover. New Jersey

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B I n R A p

MISD UM 78-9

PAYESIAN

INTERACTIVE

GRAPHICS

RELIABILITY

ASSESSMENT

PROCEDURE

BY

IRVING E, TEVIOVITZ JOHN G, MARDO

MATHEMATICAL ANALYSIS DIVISION MANAGEMENT INFORMATION SYSTEMS DIRECTORATE

US ARMY ARMAMENT RESEARCH AND DEVELOPMENT COMMAND DOVER,, NEW JERSEY 07801

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Acknowledgement s

The authors wish to thank Bruce D. Barnett, Joseph E. Bay and Edward B. Lacher for their technical support. We would also like to thank Howard G. Corneilson for his advice on incorporating the section of coding which converts the logical expression to an algebraic expression for the system reliabilities.

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DISCLAIMER

This report is issued for information and documentation purposes only. No representation is made by the Government with respect to the information in this report and the Government assumes no liability or obligation with respect thereto; nor is the material presented to be construed as the official position of the Department of the Army, unless so designated by other authorized documents.

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ABSTRACT

BIGRAP is a package of interactive graphics programs, written for use on the TEKTRONIX 4 014 Graphics Terminal connected to the ARRADCOM CDC 6500/6600 computer configura- tion. This package consists of a set of intricate programs that allows a user to input component success/failure data and a Boolean expression depicting system reliability logic for the purpose of assessing system reliability. The computer converts the logic expression to an algebraic expression for the system reliability as a function of the individual com- ponent reliabilities. A Bayesian statistical algorithm is then employed to provide the user with point and confidence interval estimates of system reliability. In addition the graphics feature of the package displays histograms and corresponding Beta distributions involved in the analysis. The programs are run sequentially as a cataloged procedure using the BEGIN/REVERT utility. This report is intended to serve as a guide to potential users of BIGRAP for operation and interpretation of results.

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TABLE OF CONTENTS

Page

1. Abstract 1

2. Introduction and Methodoloay 4

3. Description of the Main Proarams 17

4. Terminal Initialization and Loqin 20

5. Illustrative Example 2 5

a. Chanainq Number of Increments 3 5

b. Use of the Four Options" in Program MOMENT 3 9

Appendices

A. Manual Computations for a Simple Test Case 51

B. Simple Test as Run with BIGRAP 58

Update Information Request Page 6 7

References 68

Distribution List 70

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2. INTRODUCTION AND METHODOLOGY

The Bayesian Interactive Graphics Reliability Assessment Procedure (BIGRAP) is a package of interactive graphics programs written for use on the Tektronix 4014 Graphics Terminal tied into the ARRADCOM CDC 6500/6600 computer system. The package consists of a set of Fortran programs which are executed sequentially as a catalogued procedure using the BEGIN/REVERT utility. Each of the five main programs in BIGRAP, along with its associated subroutines, performs a major computational step required as part of a pseudo-Bayesian approach to reliability assessment of complex systems based on component success/failure data. This report is intended to serve as a BIGRAP user manual, as well as an introductory methodological summary providing the reader with the essentials necessary to use BIGRAP and understand the output it generates.

Reliability assessment approaches for complex systems have historically had two major weaknesses. Firstly, they provided only a point estimate of reliability and failed to provide a measure of the total uncertainty reflected by the limited component data. Secondly, the computational require- ments were unwieldy and oriented to individual systems requiring a large amount of time to accomplish with minimal computer aid. BIGRAP has neither of these weaknesses. A Bayesian reliability assessment approach is employed for com- puting point estimates, as well as confidence limits providing the required measures of uncertainty. The interactive graphics application and BEGIN/REVERT utility make the procedure easy to use, even by users unfamiliar with computer programming.

In this section, the approach underlying BIGRAP will be outlined so that the potential user will have some idea of (1) the preliminary work he will have to do before running BIGRAP to set up his problem; (2) ■ the rationale behind the computations performed by BIGRAP; and (3) the meaning of the output generated by BIGRAP.

The first step in the system reliability assessment approach underlying BIGRAP is the determination of the total number of components and component types which make up the system. Components are considered to be of the same type in this context if they are identical in design and manufacture, i.e. they can be considered, in the statistical sense, to be drawn from the same population. The meaning and importance of the distinction between the total number of components and the number of component types will become clear to the reader as he proceeds.

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The next step in the assessment procedure is the construction of a reliability block diagram which depicts the logic by which system success (or failure) occurs as a result of success (or failure) combinations of all the components which comprise the system. While it is likely that most potential users of BIGRAP are familiar with the concept of a reliability block diagram, a simple example will be provided here so that succeeding steps of the assessment approach may be more easily illustrated. Consider the simple system functional schematic provided in Figure 1.

3 MOVEMENT MECHANICAL TIMER

BATTERY 1

ACCELERA- TION \

SWITCH Hi BATTERY 2

DETONATOR

EXPLOSIVE CHARGE

FUNCTIONAL SCHEMATIC

Figure 1

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RELIABILITY BLOCK DIAGRAM

Component Name

Component Component Component • Type Type

Symbol Symbol Number

Acceleration Switch Battery 1 Battery 2 Timer Movement 1 Timer Movement 2 Timer Movement 3 Detonator Explosive Charge

A A 1 Bl B 2 B2 B 2 Tl T 3 T2 T 3 T3 T 3 D D 4 E E 5

Figure 2

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This simple system represents the author's naive conception of a possible (but improbable) missile high explosive warhead section. The system is designed so that upon sensing sufficient acceleration after launch the acceleration switch closes and the three identical movements of the timer are started. When a preset time is measured by any one of the three timers the circuit is closed between the detonator and the two identical batteries, each having sufficient voltage to fire the detonator. The firing of the detonator ignites the explosive charge completing the system mission. The system has a total of eight components, but only five component types. Figure 2 lists the different components along with their assigned component symbols and type symbols below the reliability logic block diagram for the system. The block diagram reflects that components A, D, E, one or both of components Bl and B2, and at least one of components Tl, T2 and T3 must function successfully to achieve system success.

BIGRAP was developed with the intention of allowing the user to provide, as part of the input, the system logic as depicted by the reliability block diagram. Boolean algebra provides the tools with which this can be accomplished. Once the reliability block diagram has been constructed it is easy to formulate the equivalent Boolean algebraic expression. For the sample system of Figure 1 the Boolean expression for system success, S, is

S=A*(B1 + B2)*((T1 + T2) + T3)*D*E

"or"

0*0 ■ 0 1*1 = 1

0*1 = 1*0 = 0 1+1 = 1

0+1 - 1+0 = 1 0+0 ■ o.

where the symbols "*" denotes "and" logic and "+" denotes logic. If, in this expression, one assigns to the component symbols 1 for success or 0 for failure and then evaluates the expression according to the following simple rules:

(Note; The usual associative, distributive and commutative axioms hold as well)

a value of S=l or S=0 will result in implying that system success or failure, respectively, is achieved by the assigned component successes and/or failures. For example, if one assigns A=l, B1=0, B2=l, Tl=l, T2=l, T3=0, D=l, and E=l the Boolean expression with these values substituted becomes

S = 1*(0+1)*((1+1)+0)*1*1

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which can be reduced via the above rules to

S = 1*1*(1+0)*1*1

and further to

S = 1*1*1*1*1 = 1

representing system success. As another example consider the assignment A=l, Bl=Of B2=0, Tl=l, T2=0, T3=0, D=l, E=l resulting in

S = l*(0+0)*((l+0)+0)*l*l = 1*0*(1+0)*1*1 ■ 1*0*1*1*1 = 0

showing that this latter assignment results in system failure. For readers for which the above explanation does not sufficiently clarify the process of translating the block diagram to a Boolean expression, many papers and texts in the extant literature provide more detailed explanations (see references 11 and 12).

Boolean algebra provides the means by which the system event can be described in terms of component events. The subject of reliability, however, deals with probabilities, and in particular the probability of the system success event. In fact the system reliability is defined here as the probability of system success. System reliability assessment based on component data involves the computation of point and confidence interval estimates of system reliability using success/failure data which directly estimates the individual component reliabilities. The component reliabilities are defined analogously as the probabilities of component success. Components of the same type have, by definition, the same reliability value. To proceed with the reliability assessment approach, therefore, a procedure is required by which the Boolean logic expression can be converted to an algebraic expression for system reliability in terms of the component type reliabilities. The first three programs executed as part of BIGRAP perform such a conversion for a Boolean expression of a system provided as input. The method employed therein to accomplish this is too lengthy to describe here but is adequately explained in References n and 12. The user need only be acquainted with the form of the results which will be illustrated herein.

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The conversion is accomplished in two stages. The first stage involves determination of the total number of success paths (or tie sets). For our example there are six such success paths. They are:

A*B1*T1*D*E A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E

The second stage uses this essentially expanded form of the Boolean expression and converts it to an ordinary algebraic expression for the system reliability, R ; in terms of the

component type reliabilities, resulting in

Rs = ^AVT1^ - ^A^WSs

+ 2RARBRTRDRE " ^A^VE

+ 3RARBRTRDRE " RA4RDRE where an Rx on the right side of the equal sign denotes the

reliability of component type X. This expression provides the required relationship between the system reliability and the component type reliabilities.

The Bayesian aspects of the assessment procedure are introduced at this point. The basic underlying assumption is that the unknown component type reliabilities (measured by the success/failure data) can be considered as independent random variables in the Bayesian sense, each having a prior probability distribution belonging to the family of beta distributions. The general form of the beta probability density function (pdf) for a random variable, R, is:

f g(R|A,B) = T (A+B) T (A) r(B)

= 0

RA"1(l-R)B"1for 0 <

otherwise.

where: (i)A and B are the parameters of the beta distribution ^ith the restriction that A > 0 and B > 0.

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(ii)r(.) is the complete gamma function defined by

rx-l -y. (x) =1 dy

having the property that r(x+1) = xr(x) so that for a positive integer, n,

r(n+l) = n'

If the component types are indexed 1 thru m, where m is the number of types (m = 5 for the example) the prior beta pdf of each component type reliability will be represented by f (R.l A. fB.) , i=l,...fm. BIGRAP allows the user to select from p X X JL

a variety of options for defining the A. and B. values. These

options will be described in Section 5b of this report.

The data is introduced into the assessment procedure by similarly indexing the component type number of successes and number of failures as s. and f. respectively. For a given

component type reliabilities, R., i=l,..., m, the likelihood of

observing the given data s., f. is then provided by the binomial

distribution with probability mass function given by

(si+fi): „ s. ,_ .f. Pr{sif f.; IV = 5:l H Vi d-R^ i

The likelihood expressed as a function of R. is then (si+fi): s f 1

L(IVsi'fi> = -ITTfTT- V^^V i

Application of Bayes Theorem (Principle of Inverse Probability), which says that the posterior (updated with data) probability is proportional to the product of th^ prior probability and the likelihood, results in the following:

f g(Ri|A,B.)L(R ;s f ) Posterior pdf of R. =

1 /1f6(x| Ai,Bi)L(x;siJfi)dx 0

The expression on the riaht can, upon substitution of the com- ponent type prior beta pdf and binomial likelihood, be reduced to

f (R.l A.+s. ,B.+f . ) R i1 i i' i i

10

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so that the posterior distribution of 1^ is also a member of the

beta family with posterior parameters given by

AXi = Ai + si

BX. = B. + f. Ill

It is, therefore, a simple matter to add the component success/ failure data into the assessment procedure for a given set of component type prior distributions.

Since each of the component type reliabilities is considered a random variable, the system reliability, R , which is a function

S of the component type reliabilities, is also a random variable. The exact form of the probability distribution of R clearly

s depends on the distribution of the component type reliabilities and the relationship of the component type reliabilities to system reliability as reflected in the algebraic reliability expression for R , In-depth investigations have shown that

this exact distribution can be reasonably approximated by a member of the beta family.

BIGRAP uses two methods for determining the appropriate beta fit to the distribution of R . Monte Carlo sampling and

the method of moments. The Monte Carlo approach involves generation of a large number of "trials", where on each trial each of the component type reliability posterior distributions f»(R.| AX^,BX^), i = l,...,m, is randomly sampled yielding a

set of type reliability values R1,R2,...,Rm. These values are

substituted into the algebraic reliability expression and a value of Rs, the system reliability, is obtained. This process

is repeated for the total number of trials specified by the user. A histogram depicting the distribution of the resulting system reliability values is constructed. In addition the arithmetic

mean, Rs, and sample variance, s , of the R values is computed.

A direct relationship between the parameters of a beta distribu- tion and its mean and variance is then used, with R substituted

for the mean and s substituted for the variance, to estimate

the parameters of a system beta distribution serving as a beta fit to the histogram.

In discussing the method of moments a few basics should oe recognized concerning the moments of continuous random variables in general and beta distributed random variables in

11

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particular. It is assumed that the reader is familiar with the concept of expectation. The rth moment of a random variable, X, is defined to be the expectation of the rth power of X, i.e.

th r r moment of X = E(X )

The first moment is referred to as the mean, y, of the

distribution of the random variable. Its variance, a , is defined as the second moment about the mean. Therefore,

y = E(X)

2 2 a = E(X-y P

or equivalently

a2 = E(X2)-E(X)2

This latter form of the expression for o follows from the following. If X and Y are random variables (or functions of random variables) and C and C , constants, then

E(C1X+C2Y) = C1E(X)+C2E(Y)

If X and Y are independent, then

E(XY) = E(X)E(Y)

For a random variable R having a beta distribution with pdf

given by Fg{R|A,B) the r moment is

r A+i-1 E(Ri) " * ATBTirr

»

r)

i=l

This result then yields the following expression for y and a2

of the beta distribution

y = A/(A+B)

2 m _A_ (■ A+l A % A+B ^ A+B+l A+B

12

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By solving these two expressions for A and B in terms of 2

and o the following useful formulae are obtained:

A = (1- M ) a2

B = ^' V > +y_ i a

2 By substituting estimates of y and a into these last two expressions, estimates of A and B can be obtained. This is precisely what was done in determining the beta fit to the

— 2 Monte Carlo histogram wherein R and s,, were used as estimates 9 S H

of M and a , respectively.

The method of moments involves the computation of the first and second moments of the posterior distribution of system reliability in terms of the moments of the component type reliability posterior distributions. The algebraic reliability expression for R and its algebraic square for

2 s

R are used for this purpose. The example system, with the type numbers listed in Figure 2, can be used to illustrate this procedure. The first moment of R is first determined as: s

E(Rs) = E(6R1R2R3R4R5- SR^R^R^

+2R1R2R3 R4R5 - etc.)

Using what has been stated about expectations, this can then be expressed as

E(Rs) = 6E(R1)E(R2)E(R3)E(R4)E(R5)

- 6E(R1)E(R2)E(R32)E(R4 )E{R5)

+ 2E(R1)E(R2)E(R33)E(R4)E(R5)

- etc. i

By substituting the appropriate expression for each beta moment in terms of the component type posterior beta

13

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parameters, E(Rg) can be evaluated. The appropriate

substitutions follow from:

r r AX.+j-l E(R,r) = .n. i ' j=l AX.+BX.+j-l

AXj^ 2 AX3 ^x3

+1

e-g- E(R1) = AX1+BX1 ' E(R3 ) = AX3+BX3 ' AX^BX^hl

, AX, AX-+1 AX0+2 E(R,J) =

3 AX3+BX3 AX3+BX3+1 ' AX3+BX3+2

. . 2 Similarly E(R ) is evaluated using the expectations of the

algebraic expression for the square of R , i.e., s

E(RS2) = E(36R1

2R22R3

2R42R5

2 - 72R12R

22R

33R

42R

52

+ 24R12R2

2R34R4

2R52 - 36R1

2R23R3

2R42R5

2

+ etc.)

By setting u = E(Re) and a2 = E(RM

2) - E(R )2

S S S S S

in the expressions for the beta A and B parameters, the method of moments posterior beta distribution for system reliability, R , is fully determined by the resultant A and B values; i.e., o S S

s a 2 Ms s 2

B - -Z s— + y _! s n 2 ^s CTs

The result obtained by either the Monte Carlo method or the method of moments is a beta distribution which approximates very closely the true posterior distribution of the system reliability, Rs. In each case the resultant beta distribution

14

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is completely defined by its two parameters, A and B, which will be denoted by A and B since they are the parameters of s s the posterior distribution of R . The user, however, is s ' generally performing the assessment procedure for the purpose of obtaining point or confidence interval estimates of the system reliability. BIGRAP extracts these estimates from the information contained in the system posterior beta distribution. In all cases, the mean and mode (if it exists and is between 0 and 1.0) of the posterior distribution of R are provided. These values are computed as follows: s

Mean of R = A /(A +B ) s s s s

If A > 1 and B > 1, then s s

Mode of Rs = (Ag-1)/(A +B -2)

The recommended strategy for point estimation is to take as the point estimate of R the mode when A and B are both greater s s s than (not equal to) 1.0 and the mean, otherwise.

For the purpose of confidence interval estimation, BIGRAP presently provides the lower 50, 90, and 95 per cent Bayesian confidence limits. The lower 100 (1-Y)% confidence limit for Y = .5, .1, or .05 is defined as the value of R satisfying the following:

Y = / Rf(R |A ,B )dR n B S ' S ' S' S

where the A and B that are used result from either the Monte

Carlo method or the method of moments. Precise numerical integration routines included in BIGRAP set up and interpolate a table of Y vs R to determine the appropriate value of R.

For a particular system configuration to which BIGRAP is being applied for the first time the user may wish to employ both the Monte Carlo approach and the method of moments. By comparing the point and confidence limit estimates resulting from the both methods the user can satisfy himself that the assumptions involved in the method of moments approach (use of only first two moments and a beta fit to system reliability distribution) do not introduce significant errors. In subsequent applications to the same system configuration the user need only apply the method of moments should the comparison be favorable. If, on the other hand, there is significant disagreement between these results, or if the beta distribution in the Monte Carlo approach does not appear to fit the histogram, the user may then choose to continue with the Monte Carlo approach. In the latter case the user should make use of the histogram itself, rather then its beta fit, to extract empirical point and interval estimates.

15

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The succeeding sections of this report present a detailed description of the operation and structure of the BIGRAP software. Instructions for job control and input are also provided. Several examples of the use of BIGRAP are presented. In addition the complex manual computations, which are the alternative to employing BIGRAP, for a simple system configuration are exhibited to emphasize the value of the BIGRAP package.

The reader interested in more details regarding the theoretical basis for BIGRAP should look to the cited references and in particular Reference 14.

As a final introductory comment, the authors wish to point out that a large amount of work was performed in comparing the results from BIGRAP to other approaches to reliability assessment both classical and Bayesian. For the restricted cases (in the sense of system configuration complexity) to which these other approaches could be applied, BIGRAP performed at least as well and, in most cases, better. So whether the reader considers himself (or herself) a Bayesian, Classicist, or "middle-of-the- roader" the assessment algorithm of BIGRAP should prove satisfactory.

16

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3. DESCRIPTION OF THE MAIN PROGRAMS

The Bayesian Interactive Graphics Reliability Assessment Procedure is made up of five main computer programs (B0LN1, B0LN2, B0LN3, MOMENT, MONTI) which will be described here:

Program B0LN1 - Uses as input, the Boolean expression of a reliability block diagram in free form. The program transforms the simple expression to integer form by comparing each element in the expression to the list of special characters (plus sign, asterisk, and right and left parentheses) and components and places the number of the list that equals the element of the expression in the same position as the element. The program then goes through the expression and stores the number of sections and the locations of the plus signs and left and right parentheses for each set of parentheses. The results of the above operations are written on a disk for use in program B0LN2.

Program B0LN2 - Reads the disk output from program B0LN1 as input. The program expands the expression in the conventional manner to ascertain all the success paths. As each path is derived, it is compared to all previously generated paths. If the newly derived path contains or is equal to any previously generated path, the new one is eliminated as a redundancy. If the newly derived path is contained in any other previously generated path, the new one replaces the older one, which is then eliminated as a redundancy. If neither of the above is found to be true, the newly ascertained path is added to the list of non-redundant paths. The results are then written (on both disc and printout).

Program B0LN3 - Converts Boolean logic expression to an expanded algebraic reliability expression. Constructs a Fortran subroutine, on TAPE 12, for calculation of system reliability using the algebraic expresison, passes this subroutine to program MONTI, passes the algebraic reliability expression to output and program MOMENT on TAPE 7.

Program MOMENT - Allows the user to select one of four options. Option 1 uses the algebraic reliability expression from program B0LN3. It then determines and stores the square of the algebraic expression and formulates the system distri- bution 1st and 2nd moments as functions of the moments of the component distributions. These results are then used to determine the equal component prior beta parameters A' and B*, which yield a uniform prior distribution for the system reliability. It also computes the posterior beta parameters for each component and substitutes these results into the expressions for the system moments. The method of moments estimates of system posterior beta parameters are then computed.

17

Page 22: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

In Option 2 and Option 4 the user provides the prior beta parameters (either equal or unequal) for each component. There is, of course, no need for a solution to the momfent equations prior to performing the method of moments estimation procedure.

In Option 3 the moment expressions are set equal to user specified 1st and 2nd prior moments. These equations are then solved and the same procedures are followed as in Option 1.

Program MONTI - Uses the component posterior beta parameters for each component as well as the method of moments estimates of the system beta parameters as input. The component parameters are used to define beta distributions for each component. Monte Carlo simulation is then performed by sampling in turn each of the component distributions for a component reliability value; substituting these values into the system algebraic reliability expression (generated in B0LN3), generating a system reliability value on each Monte Carlo trial. After a sufficiently large number of trials, a histogram of system reliability values is obtained, in addition to the mean and variance of the generated system reliability values. It then computes lower confidence limits for system reliability based on the method of moments and Monte Carlo results. Finally the histogram is displayed on the Tektronix screen with a beta curve fit from the mean and variance superimposed. A useful feature of program MONTI is the capability of generating additional histograms for the same set of inputs varying either the number of histogram cells (increments) or the number of Monte Carlo trials (samples). The random number generator subroutines, RDMIN and RDMOUT, are also employed to avoid the use of the same or overlapping set of random numbers on subsequent runs with the same set of inputs. These features are illustrated in section 5 of this report.

The present form of Programs B0LN1, B0LN2, and B0LN3 were based on programs originally written by Howard Corneilson. Each of his original separate programs were run as batch jobs. The modified programs are used interactively with the graphics terminal and are run sequentially using BEGIN/REVERT.

Program MOMENT was based on a batch program written by Bruce D. Barnett. The BIGRAP form of the program derives its input directly from program B0LN3 without the need for the user to provide the algebraic expression.

Program MONTI was based on two programs written by Irving E. Teviovitz for the 274/1700/6500 large scale refresh graphics facility. One program illustrated a user specified beta distri- bution probability density function and the second program il- lustrated a beta random distributed histogram. The two programs were combined and converted for use on the Tektronix terminal. The JBETA subroutine in MONTI for numerical integration of the beta distributions was developed by Joseph E. Bay through modification of subroutines used in program RELY (Neff 1969).

18

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The BEGIN/REVERT utility, which automatically executes all the job control statements that are needed to run these programs, is a set of programs developed by the University of Washington.

19

Page 24: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

4. TERMINAL INITIALIZATION AND LOGIN

A typical Tektronix 4014 Graphics Terminal set-up is pictured in Fiaure 3. A complete description of the terminal and its operation can be obtained in Reference 3.

The purpose of this section is to acquaint the potential user with some basic information required to ooerate the 4 014 terminal in connection with use of BIGRAP.

Fiqure 4 nrovides a description of the keyboard con- figuration of the 4 014 terminal.

20

Page 25: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

s I * l i , s _ « s *" i f ^

Page 26: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

>

o

3 <

U- 2

'J

<

o

o o

z cc O g li. CE

& < O iu

o '-i ^ LU LU

Q ^ Z

u. UJ Q O Q Z ^ O < g O c

o

O UJ

g o a.

[rrniTJi

F0

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CN

z -- _J ^o _J UJ < < cc o. u o

>

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a k

vQ

z cc 11

a OT LU

CC o ^-*^— "" —i

--/ II 1

» •• 1 1 ^ Q. 1 ' _1 I

LL

Q

LO

22

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A

s H] la 0

(J

N

—? > o t- O

0) >-l

•H fa

E M

"4-1 0) 0 EH

n o (O-H

mo

-P-P 3

in •H

a e o in u

EnrH O

Page 27: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

The following procedures are required for Terminal initialization.

1. Place the LOCAL/LINE switch to LOCAL (the terminal will be isolated from the computer and causes keyboard inputs to be executed by the terminal).

2. Turn the Terminal ON (the power switch is on the front lower right of the console (one foot from floor). The green power light on the left of the keyboard will light and the display screen will become bright after a few seconds,

NOTE: At turn onf the terminal is in Alpha Mode with the cursor at HOME position with normal (large character size and is in synchronous communications mode.

3. Turn on hard copier (if one is available). Erase one display by pushing the RESET-PAGE key (at least one erase after power-up is required to start the interface).

4. Set the following keyboard switches:

CODE EXPANDER TO OFF CLEAR WRITE TO OFF

5. Set the interface control switches

Rotary baud switch to 300 for 300 baud rate (rear of terminal) ASCII/BCD switch to ASCII (rear of terminal)

6. SHIFT, RESET-PAGE keys are depressed on the keyboard simultaneously. This will initialize the Terminal, by placing initial conditions on the Terminal circuits.

7. Press CTRL, SHIFT and P keys - (for local echo).

8. Press the followinq three keys sequentially: RETURN ESC : (For small characters)

9. Put LOCAL/LINE switch to LINE

10. Remove grey phone from the modern cradle, switch phone to TALK. Phone select switch under table to be in clockwise position marked "OPT".

11. Dial up (to connect to CDC 6500/6600)

12. When the computer gives an audible tone, the button marked DATA is pushed and the phone is hung up.

23

Page 28: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

13. INTERCOM sign-on (LOGIN) procedures will then be re- quested on the terminal screen and be responded to by the user as illustrated in figure 5.

24

Page 29: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

5. ILLUSTRATIVE FXAMPLE

INTERCOM commands to initiate the B1GRAP procedure also il- lustrated in the same figure.

To show what happens next, the example from the Introduction (Section 2) will be used.

The screen is cleared and information shown on page 27 is requested. The user's inputs are underlined.

The name, type, number of successes and failures of each component is entered one at a time, only when prompted and each followed by a return.

Note the warnincr for entering the Boolean expression.

At the end of the nage a Copy may be made and/or the "ESC" key followed by the "Return" key must be depressed (this sequence must be followed at the end of every page).

Systems messages are orinted out on page 3n.

The output from BOLN 2 and BOLN 3 are batched to terminal specified above. This output consists of system success paths shown on page 2B and algebraic reliability expression, pane 29.

Various options are requested on page 31.

A "Copy,Esc,Return-(C,E,R)" sequence is required here. Various results are shown on nage 32.

A "CEfR" sequence is used at end of "THE VAR OF RS= ".

On page 3 3 RANDOM START is any ten diait inteqer number. The NUMBER of Increments and Samples are floating point numbers. A "C,E,R," sequence is used at end of "RANDOM END IS ".

The histogram and distribution curve is shown on page 34. A "C,E,R" is required at the end of cur e. Next follow directions on paae 34.

Pages 3^ to 38 show how the histogram chanqes as the number of increments change (line 2 of paae 35 and 37.)

The display on nage 3rj is shown when the cursor is placed on line 3 and the number "3" is nressed.

Pages 3 9 to 50 show how Options 2,3 and 4 are used.

25

Page 30: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

03 (D C

> 1 in 5- O • D- Of

^ X o X 3

c X iSi o z> in o ID <c a: 3 o. Ul 13 i- 1 Qi ZI • Ul UJ »-«WH E 1-

r*-^- * <i: z: <EX • z z: LJ 1-00 to ►-» <r<s>Lf> o CK Sg Q\ ♦ o UJ tm

tHO) ^1 v> ^JOO J M o 111 n Q£ CDZ: a: h-UJLxJ <r»-« UJ M

ZI-E: UJO I- m 0<E»-« ^JO z: n OOI- Q-^J OJ ■i

• ^^

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CO l-QN- "0 c

0) <L»-i 1 1- 4-)

Z:Q:Q£ X »-«UJO w

tno. QZ3N LJ Q.O OX»-i<& oi-riro ot-«o *

00

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c o Q] M

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Page 31: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

H

in

I 4

iif\ i M

>

Ul u>

S ?| 3 O ■ M

* I * S *

•V

m« tft no « n « rex ,-, r.w P - 5 «ft •- u.

lilts

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mi*- w nir- r «j r I _- w w o UO ifc I-I- ui in ui

rl 0 - 2 ^ f^1 | ft' 5 I1' 5

OC^-NU|-^- U1~U

S -- S ^ $ ^ g

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Page 32: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

1/ > 1/

LL u.

C

6'^ tr c\ J i' i- _j <■

c Q a

\f 5, Lf C u a C1 r rv U. u h- i—

u u « * t- ^ 4

a u rv

u Q <

rv. cv IJJ a a n u * # i K

n

c

►- I—

at a a: a

28

Page 33: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

UJ

IT > (Si

O

c LU

c

2

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o cr U. a >

z c

< O UJ

Q- C

t-

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C^ u • <T a CV a 2 C UJ » C e c o- ir -j J U.

cr IT 3 vC 1- u C • c l c -J i^

LL1

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CJ 29 ■ I;

Page 34: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

m •-• **

| S Si s I 3 35 2UI Ulg

: 1 $• I » bill On

3

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i w> utw>

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30

Page 35: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

O)

llJ

in

U)UJUJ

iAJV>UI B->-E

C DC

OCZQ.

Q_ock: LAJO

O QC

cxuna

QLUilx.Z3

CO UIUJ

LJ CO.

o

=)3

00 UJUJ H

U.IJL.Q

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o UIUJZ

ZDZ3»-«

a. OL

31

Page 36: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

Ul *-i

o

♦-i <E

3 1-4 O Q. D- UJ o. X O o UJ O o

r^ a> ifi a: *-• c* O UJ 21 z i- O o u. Q o o <r a: UJ UJ o U) in

UJ o UJ

Q. Q. QC tk: O o Ul

'<- 1- % n i^ z <s> ru •^, =3

Q-I^- o> O o • • o

(ft

U.UJO UJQ-I-UJ

W

O ►J nn y* TO) o ^^-i <s><» u. cu^ U. CTLOCT)-^-

OHD O Lr><s>Lnooa3 <n CXJOJ n^o>oor- ck: ♦ • o • •n^-^-i UJ «-« o nnjoooo® i- "T CO •» -• • * <D UJ H- « c Ul <c a: oo <r oo Ul t~l- DL l-l- II N

1- J-J M <L -J—I <E<E</>W t~ <r<E o 33Q:tt:u> Ul Z3 Z3 z oo Q: O) OO t-l UIUJLI-U.

UJUJ w OOLi_ CL. "^ unn o O <na) •-••—'ZUI •-< *-t*--i w <coa: Q; 1- o)a>ujo<E CL <xca ^J

(^

<rraaE:E::>

UJ UJUJ UIUIUJUJUI X XX Ul xxxxx 1- H-i- s l-l-l-l-l-

32

Page 37: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

ru r> M If T r^ \n r-

oo r- iv

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a1

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Page 38: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

i ¥-

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ii r « « o

s I?? at ZKlfibi ooa «<! (A .-woo

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Page 39: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

•a (U '0 U3 0) ^1

!/) a.

at ^^ ■w •*J 0 '-» to r o ^ PO

6 3 r o U U U o 0) V c -C -Q M Jj e

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no tu U) CO ai n Hi

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Page 40: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

r <iZo o z I I Mbiuj gzEtnw once a

U|<->bJOO if »-*- So »-s- 0<tMXX

i r

36

Page 41: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

ao ru -r in oa u) m rt IA ■» CO (J3 co r>- r-

Ul U) 10 a> CT y> «^ «-« n ■* 00 U3 oo i^ r^

3 O

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O o U- z: o " O o o o • f o>

U) «. t- t- l~ -* ss 1 UJ UJ

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37

Page 42: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

z o

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I

z §*« ■-•30

Z I I ►-* UJ UJ

*UJ(J o

30 l-t~ o<ia>xx

n. v

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Page 43: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

4J C 0) e o xn T. t-

B LJ ITS

fji O 0 E wi (A a, sra: r* V>UJUJ

UJU>LLI in 1-5-E c UJOXC

s: a: 4-1 <EQ<E Qj c^za. o <ro

CLOCt 1-1 UJO 0 OL<S)y-* CM

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0 Q.<E»J QJ <C U3 flC»Jt-Z3 3 o<ro>o

Q^Oi-tZ XI Q.UJli.=}

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^1 (k a: U4M

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39

Page 44: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

-J 9® o 99 Ij- <S>©

9U) o> e&cu on ♦ ♦ in U) t- Ui

a: oc <r oo Q. l-l-

<c -J-J i- <c<c LJ 33 m OO

LULU oc o OJW) t-t »-«»-l QC Q. <Eca Ui UJLU 3C XX

o

UI El

liJ X I-

C3

3

LU

cocy oo r- r*-^r-Lr> Lnu)oocoLr> ♦ •^TLn-T-*

«s>aioococs>

oo H M

3=)Ck:Q!:u) OO CK LULULL.UL

OOix. van o •—ti-^ZLU

cntr»Luo<c <roc»E:E:3 UI LULU LULU XXXXX K I-1-1-1=

40

Page 45: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

in ao i/>

1/1 S r- co r- r-

S CO « r-

_l

8 GO

a

*- in

5 5 ■k

t

PS Z ui r <n

ZU1

«n QC UIU. ■uo

ZTUJ CO

a

(n

u o

o X

s

M 1^

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i * * o o o o o o

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a. x

in

ui

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UI UJ I I

UJ

at i» UJ ui

i 3

o u a 5

^ ^ ^ UJ UI UI UI u

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a 00 > z r r <r in Ui ui UI o «nn o o c> •Of oc OL Q

UI ru UI UI UI i- -■a: a a a s s z X X c t- »- i- UI ■ <s> a> m o> a in ot o> m o tAm^r u. "SS DC

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41

Page 46: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

Ul

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Page 47: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

UJ

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en;

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43

Page 48: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

<Ji

Ul

*J 901 o U)I^ u. UD<S> cnin

U) ▼ OJ a: • • Ul c^ H- UJ z: <x: ct <t oo Q. l-l-

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Page 49: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

n M •« -r oo r-

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45

Page 50: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

E

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46

Page 51: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

u>

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^J -J —J WMJ ^*^ I— - - - - -

47

Page 52: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

^& 09 C& Cd Cd O 4D <!D <& C& 9<9<dCS>0 C&€S>0<S>® QJ»00<& ® O <D ® G> Cd en CE) CD 49 ® 09 i- • • * • * 22 3 fum^-®ir» LJ

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48

Page 53: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

p- r- m n n ra ♦ t- d> <■ in u>

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49

Page 54: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

s

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puiy

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50

Page 55: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

APPENDIX A

MANUAL COMPUTATION FOR A SIMPLE TEST CASE

51

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MANUAL COMPUTATIONS FOR A SIMPLE ^EST CASE

The benefits of BIGRAP can be readily demonstrated by comparinq the ease with which BIGRAP is used with the cor- responding alternative manual computations. In this appendix the manual computations required to perform just the Method of Moments Bayesian reliability assessment for a simple system configuration will be compared to utilization of BIGRAP. The reader is reminded that BIGRAP also provides the Monte Carlo option for which manual computations are virtually impossible.

52

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Example:

a. Reliability Block Diagram:

b. Boolean Expression: A*B*(C+D)

(Note: For more complex systems conversion of Boolean expression to algebraic expression is a cumbersome task without the aid of a computer program).

c. Component Descriptions:

Data Name Type, Ri Successes 'si Fai lures. fi

A Rl 19 1 n R2 17 3'

c R3 R3

D 35 5

d. Algebraic Reliability Expression for System Reliability, Rs:

Rs = 2R1R2R3 - R^R*

e. Square of Algebraic Expression:

R^ = 4R^R^R^ - 4R?R^R^ + R^RIR* s 123 123 123

f. First Moment of System Reliability Distribution in Terms of Moments of Component Reliability Distributions:

E(Rg) = 2E(R1)E{R2)E(R3) - E (R^ E (R2) E CR3)

53

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g. Second Moment of System Reliability Distribution:

E(R^) = 4E(RJ)E(R2)E(R3) - 4E(R^)E(R^)E(R^)

+E(RJ)E(R^)E{R3)

h. Find Component Prior Beta Parameters, a' and b'. Which Yield Uniform Prior Distribution for System Reliability

(1) Substitute E(Rf) = . H. ,^'tJT1.,

for each expectation appearing in first and second moment expressions above.

(2) Set resulting first moment expression equal to 1/2, the value of the first moment of a uniform distribution on the interval (0,1).

(3) Set resulting second moment expression equal to 1/3, the value of the second moment of the uniform distribution.

(4) Solve the resulting two equations for the two unknowns, a* and b*. For this simple system the two equations to be solved are:

E'V =2(5?^) -(J^BT) a'+b'+l = 1/2

and

TPIT>2\ - * ( a' W a'+l i3 A( a' ^ 3 r a'+l >> 3 a •+2 MV " 4 V+b'-' la'+b'+l^ " 4U,+b^ t-a'+b'+l^ a'+b*+2

■ fa') (• a'+l ) f a,+2 )f a'+3 ) 1 ^a'+b"1 ^a'+b'+l7 l a'+b,+2/la,+b,+3; ' 3

To solve these non-linear equations without the use of the computer is a difficult and time consuming task. Iterative procedures such as Newton's Method must be employed.

54

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The solutions for this example are:

a' = 1.2382 b" = 0.3965

The values are used as the prior beta parameters for all components and result in an approximately uniform prior distribution for system reliability.

i. Component Posterior Beta Parameters:

a1 = s1 + a' = 19 + 1.2382 = 20.2382

b. « f. + b' » 1 + 0.3965 = 1.3965

a2 = s2 + a' = 17 + 1.2382 = 18.2382

b2 = f2 + b1 = 3 + 0.3965 = 3.3965

a3 = s3 + a' = 35 + 1.2382 = 36.2382 '

b3 = f3 + b' = 5 +0.3965 = 5.3965

j. Component Posterior Moments Needed in First and Second System Moment Expressions:

ECV - T-TtT ' lVl\l2n = 0.93545 1 11 21.6347

2 al al+1 E(Ri) = T-^T ' . -UK 4.1 = 0.87774 1 al+D1 a.+b.+l

a2 E(RT) = —TC- = 0.84301 2 a +b

2 a2 a2+1 E(R^) = —fr— . —rf—rr = 0.71651

2 a2+b2 a2+b2+1

55

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E(R3) = a3+b3 = 0.87038

2 a3+1 E(R3) = E^- ^TbTTT = 0.76022

3 2 a3+2 E(R3) = E^3)' S^T2 = 0.66620

4 t ao+3 E(R3) ^^'a^I = 0.58565

k. First Posterior Moment (Mean) of System Reliability:

Substitute the results in j. in first moment expression provided in f.

E(Rs) = 2(0.93545) (0.84301) (0.87038)

- (0.93545) (0.84301) (0.76022)

= 0.77325

1. Second Posterior Moment of System Reliability:

Substitute the results in j. in the second moment expression provided in q.

E(Rg) = 4(0.87774) (0.71651) (0.76022)

-4(0.87774) (0.71651) (0.66620)

+ (0.87774) (0.71651) (0.58565)

= 0.604851

m. Posterior Variance of System Reliability;

Var(R ) = E(R2) - E2(R ) S S S

= 0.604851 - (0.77325)2

= 0.006936

56

Page 61: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

n. System Reliability Posterior Beta Parameters, a and b ' s s

E2(R )(1-E(R )) Use a = ^ E(R )

Var(Rs) s

E(R )(1-E(R ))2

bs = Var(R ) + ^V"1

Hence as = 18.77365

bg = 5.50523

o. Beta Density Function of Posterior Distribution of System Reliability:

fR(RJ a .b ) = f0(RJ 18.77365,5.50523) P S S S D s

r(24.27888)R 17-77365(1-R )4.50523 s s

r(18.77365) r(5.50523)

p. Best Estimate of System Reliability:

In this case the posterior distribution has a mode less than 1.0 so that the mode is the best estimate. *

a -1 Mode of R = —|r T = 0.79778 (Best Estimate) s a +b -2 s s

q. 100(1-Y)% Lower Confidence Limit on System Reliability:

Find R such that

R / f (R | a ,b )dR = Y J s1 s' s s o

(Note: Here aaain manual computations are difficult requiring complex interpolation schemes of tabled incomplete beta values or computer numerical integration algorithms)

*See page 15 for explanation (underlined line)

57

Page 62: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

APPENDIX B

THE SIMPLE TEST CASE AS RUN WITH BIGRAP

58

Page 63: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

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Page 64: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

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Page 65: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

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Page 66: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

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<r o: en </> u) ixi o Q

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62

Page 67: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

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63

Page 68: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

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Page 69: BAYESIA INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT · A*B1*T2*D*E A*B1*T3*D*E A*B2*T1*D*E A*B2*T2*D*E A*B2*T3*D*E The second stage uses this essentially expanded form of the Boolean

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s

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66

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BIGRAP ROrTINE UPDATE INFORMATION RFOUEST PAGE

If you would like to receive any future revisions of this manual automatically or desire extra copies, please fill out the appropriate form below and return to:

IRVING E. TEVIOVITZ MISD/MAD, BLDG. 3 53S ARRADCOM DOVER, NJ 07801

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Please send may any future revisions to BIGRAP manual,

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Please send me BIGRAP Manual(s).

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■■

REFERENCES

I, Beqin/Revert Reference Manual, Manaoement Information Systems Directorate, (MISD) , Bulletir NR. ""fi-S, March 28, 1976.

Manual, (CDC), (60100000), Revision AE, ^eoruary 7, 1975.

3. Digital Systems Handbook for Scientists and Engineers, MISD, Information Report NR. 71-21, Updated through November 19 77.

4. Fortran Extended Reference Manual, CDC, (60305600), Version 4, Revision J, March 5, 1^76.

5. Intercom Reference Manual, CDC, (60307100), Version 4, Revision G, May 16, 1976.

6. Math Science Library - (Description Manuals) Volumes 1-8, CDC, (60327500), Revision B, July 20, 1973.

7. Plot - 10, Terminal Control System, Tektronix, Inc, User's Manual No. 062-1474-00, March 10, 1975.

8. Scope Reference Manual, CDC, (60307200), Version 3.4, Revision L, December 31, 1975.

9. Scope 3.4 User's Guide, CDC, (60358700), Revision A, November 23, 197 3.

10. Barnett, B. D., "Quest - A Program For Estimating System Reliability By a Monte Carlo Method," Picatinny Arsenal Report, Data Processing Systems Office-6, (DPSO), June 1966.

II. Corneilson, H. G., "A Computerized Procedure for Expanding Complex Boolean Expressions Into Tie-Sets" SMUPA-NR-3- 67, 1968.

12. Loniewski, E., J. Mardo, and A. Ricciardi, "Systemex - A Computer Program for Reliability Mathematical Modeling," Picatinny Arsenal Report, SMUPA-NR-10-68, July, 1968.

13. Mardo, J. G., P. V. Z. Cole, G. Seibel, and A. R. Stephenson, "A Tri-Service Bayesian Approach to Nuclear Weapons Reliability Assessment," Picatinny Arsenal Technical Report 4359, April, 1972.

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14. Mardo, J. G. and T. G. McCarthy, "Bayesian Estimation of Reliability for Components with Independent, Normally Distributed Characteristics," Picatinny Arsenal Technical Report 4 670, December 1974.

15. Mood, A. and F. Graybill, Introduction to the Theory of Statistics, McGraw-Hill Company, New York, 1963.

16. Neef, T. A., "Rely - A Program for Estimating Overall System Reliability Based on Component, System and Flight Data," Picatinny Arsenal Technical Memorandum 1891, DPSO, March, 1969.

17. Raiffa, M. and R. Schlaifer, Applied Statistical Decision Theory, Graduate School of Business Administration, Harvard University, Boston, 1961.

18. Shooman, M. L., Probabilistic Reliability; An Engineering Approach, McGraw-Hill Company. New York, T96T:

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DISTRIBUTION LIST

topv No,

Commander: US Army Armament Research and Development Command AT^N: DRDAR-MS, Mr. D.

DRDAR-MSM, Mr. B. DRDAR-MSM, Mr. I. DRDAR-MSE, Mr. R. DRDAR-QAS, Mr. J. DRDAR-QA, DRDAR-TSS,

Dover, NJ 07801

L. Crobstein D. Barnett E. ^eviovitz Isakower C. Mardo

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UNCLASSIFIED SCCURITY CLASf.iriCATION OF THIS PAGE (TtTinn llnln V.nlrr-d)

REPORT DOCUMENTATION PAGE RKAD INSTRUCTIONS BEFORE C.OMPLKTJNd FORM

I. REPORT NUMBER

MISD User Manual UM ',8-9 2. OOVT ACCESSION NO 3. RECIPIENT'S CATALOG NUMBI R

*. TITLE f»nd Subdd.)

BIORAP - BAYESIAN INTERACTIVE GRAPHICS RELIABILITY ASSESSMENT PROCEDURE

5. TYPE OF REPORT a PERlob COVERFD

USER MANUAL (FINAL) 8. PERFORMING ORG. REPORT NUMBER

7. AUTHOR(-«;

IRVINO F. TEVIOVITZ JOHN G. MARDO - DRDAR-QAS

8. CONTRACT OR GRANT NUMBERC")

9. PERFORMING ORGANIZATION NAME AND ADDRESS

Manarrement Information Systems Directorate ARRADCOM, Mathematical Analysis Division never, NJ 078 01

10. PROGRAM ELEMENT, PROJECT. TASK AREA & WORK UNIT NUMBERS

II. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE

July 1078

U. MONITORING AGENCY NAME A ADDRESSf//d/»ar«n( Irani Conlrolllng Otllct)

13. NUMBER OF PAGES

75 IS. SECURITY CLASS, (ol Ihlt report)

UNCLASSIFIED I5a. DECLASSIFI CATION/DOWN GRADING

SCHEDULE

16. DISTRIBUTION STATEMENT (ol Oil* Reporl)

Annroved for Public Release; Distribution Unlimited

17. DISTRIBUTION STATEMENT (ol the abmlract ontarmd In Block 20, II dlflormt horn Report)

18. SUPPLEMENTARY NOTES

19. KEY WORDS (Continue on reverie aide it necemeery and identity by block number)

BIORAP Assessment Component Bayesian Procedure Success Interactive Computer Failure Graphics Tektronix 4014 Boolean Reliability ARRADCOM Logical

Statistics Confidence Histoarams Beta Algebraic

20^ ABSTRACT (Coattoum an rerar— alii* tt vmamtmmf mid Idenlllr by block number)

BIGRAP is a package of interactive afaphics procrrams, written for use on the TEKTRONIX 4 014 Graphics Terminal connected to the ARRADCOM CDC 6500/6600 computer confiauration. This oackaae con- sists of a set of intricate proarams that allows a user to input comnonent success/failure data and a Boolean exnression depictina system reliability locric for the purpose of assessinn svstem reliability. The computer converts the loaic expression to an ■

DD.^1473 EDtTION OF » MOV «8 IS OBSOLETE UNCLASSIFIED

tBCURITV CLASSIFICATION OF THIS ^AOE (Wt^n Dal* Entered) «t I

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UNCLASSIFIED

20. Abstract (continued)

alqebraic expression for the system reliabilitv as a function of the individual component reliabilities. A Bayesian statistical alqorithm is them employed to provide the user with point and confidence interval estirates of system reliability. In addition the aranhics feature of the package displays histograms and correspondinrf Beta distri- butions involved in the analysis. The nroqrams are run sequentially as a cataloaed nrocedure usina the BECIN/REVET'.T utility. This renort is intended to serve as a quide to potential users of BTHRAP for operation and internretation of results.


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