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Work Measurement & Standards
Applied Management Science for Decision Making, 1e Applied Management Science for Decision Making, 1e © 2012 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD© 2012 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD
Micro-Approach School of Job DesignMicro-Approach School of Job Design
In 1820s England, the first efforts to cut costs and increase productivity began.
Frederick Winslow Taylor ( 1881 ) organized the research findings and developed more formal methods.
He is considered to be the Father of Scientific Management.
THE TAYLOR SCHOOL / THE TECHNICAL - PHYSICAL SCHOOL
Taylor School of Job Design
• Eliminate idle time for workers and machines.
• Eliminate duplication of effort.
• Streamline the flow of work through the firm.
• Rearrange task sequences for more efficiency.
• Reduce jobs to short-cycle , repetitive ones for higher productivity and eventual replacement of humans with machines.
• Systematic reduction of skill requirements in each job.
ASSUMES WORKERS SOLE MOTIVATION IS MORE MONEY
TENETS
Work Measurement & TimeWork Measurement & TimeStandardsStandards
Direct Time Study
Predetermined Time Study
Work Sampling
Performance Ratings Allowance Factors Sample Size Determination
Observation Schedules Interpretation of Findings Sample Size Determination
Therbligs The MTM Product
Direct Time StudyDirect Time StudyEXAMPLE
Problem Statement
Twenty workers who perform the identical job are selected forthis time study. Each worker will be timed over five (5) cycles.Assume that the total observed time will eventually equal 400 minutes.
Requirement
Develop a time standard for a particular worker.
THE WORKER SAMPLE CAN BESELECTED FROM A SINGLE FACILITY
OR IT MAY BE A COMPOSITE SAMPLE SELECTED FROM
SEVERAL FACILITIES
Direct Time StudyDirect Time StudyEXAMPLE
1. COMPUTE THE OBSERVED TIME
OT = SUM OF ALL OBSERVED TIMES
NUMBER OF OBSERVED CYCLES
= 400 MINUTES
100 CYCLES= 4.000 MINUTES
OBSERVED TIME IS COMPUTED THREE PLACES TO THE RIGHT OF THE DECIMAL POINT
akaAverage
CycleTime
Direct Time StudyDirect Time StudyEXAMPLE
2. COMPUTE THE NORMAL TIME
NT = OT x PR
THE PERFORMANCE RATING ADJUSTS THE OBSERVED TIME TO WHAT THE NORMAL TIMESHOULD BE FOR A PARTICULAR WORKER.
EVERY WORKER IS ASSIGNED A UNIQUE PERFORMANCE RATING BY THE TIME AND MOTIONANALYST.
*
Performance RatingsPerformance Ratings
PR = 1.0 denotes an average worker.
PR < 1.0 denotes a fast worker.
PR > 1.0 denotes a slow worker.
PERFORMANCE RATINGS ARE ESTABLISHED FOR EACH WORKER.IT IS STILL SOMETHING OF AN ART AND CONSEQUENTLY CAN BE
CHALLENGED BY UNION OFFICIALS. THOROUGH DOCUMENTATION OF ALL PERFORMANCE RATINGS IS ESSENTIAL.
Direct Time StudyDirect Time Study
2. NORMAL TIME ( continued )
A particular worker in this time study has been assigned a performance rating of 85% .
This means s/he has been judged to be a fast worker and thus should be held to a bit shorter normal time , or higher level of performance.
NT = ( 4.000 ) x ( .85 ) = 3.400 MINUTES
Direct Time StudyDirect Time StudyEXAMPLE
3. COMPUTE THE STANDARD TIME
ST = NT
1 - AFNT + [ AF x OT ]
**
* THE ALLOWANCE FACTOR IS ASSIGNED TO ALL WORKERS PERFORMING THEIDENTICAL TASK. IT INCLUDES EXTRA TIME FOR PERSONAL NEEDS, FATIGUE,
RECURRING AND UNAVOIDABLE WORK DELAYS, AND CLEANUP BETWEENVARIOUS OPERATIONS
Allowance FactorsAllowance Factors
Constant Allowances PERSONAL……………5%
FATIGUE……………....4%
Variable Allowances STANDING………….2 to 4%
MENTAL STRAIN….4 to 8%
TEDIOUSNESS…….2 to 5%
NOISE LEVEL……...2 to 5%
HEAT / HUMIDITY…0 to 10%
POOR LIGHTING…..2 to 5%
EXAMPLE
Direct Time StDirect Time StudyudyEXAMPLE
ASSUME AN ALLOWANCE FACTOR OF 13% WITH THE CHOICE OF FORMULA LEFT TO THE DISCRETION OF THE ANALYST.
3. COMPUTE THE STANDARD TIME ( continued )
ST = 3.400
1 - .13=
3.400
.87= 3.900 MINUTES
ST = 3.400 + [.13 x 4.000] = 3.400 + .5200 = 3.920 MINUTES
QM for WINDOWSQM for WINDOWS
Work MeasurementWork Measurementandand
Standard SettingStandard Setting
For simplicity, we assume that each of the five workers observed had an actual performance time of 4 minutes
The particular worker that we are setting a standardfor, has a performance rating of 85%
This worker performs a short cycle job with onlyone (1) particular activity or element involved
Average cycle time or OT ( observed time ) = 4.0 minutes
Normal time ( OT x PR ) = ( 4.00 x .85 ) = 3.4 minutes
Standard time = [ NT / ( 1 - AF ) ] = [ 3.4 / ( 1 - .13 ) ] = 3.91 minutes
Direct Time StudyDirect Time StudySAMPLE SIZE DETERMINATION
Suppose we want to know the number of cycles we must observe in order to obtainan average cycle time that is 95% certain to fall within +/- 5% of the actual averagecycle time for all workers performing thisjob or task within a job.
μ
Direct Time StudyDirect Time StudySAMPLE SIZE DETERMINATION
Let’s say you did a pilot time study in whichsix workers performing the identical job ortask were observed over two cycles each
for a total of twelve cycles
Average cycle time for this sample turnedout to be 3.000 minutes with a standard
deviation of 1.000 minute
x = 3.000
s = 1.000
_
Direct Time StudyDirect Time Study
SAMPLE SIZE
DETERMINATION
THE FORMULA
n = z s
x
2
where:
x = THE SAMPLE MEANs = THE SAMPLE STANDARD DEVIATIONε = ALLOWABLE OR TOLERATED ERROR EXPRESSED AS A DECIMAL ( 5% = .05 )z = NUMBER OF STANDARD DEVIATIONS FOR THE DESIRED CONFIDENCE LEVEL ( 95% = 1.96 )
ε_
Direct Time StudyDirect Time StudySAMPLE SIZE DETERMINATION
n = 1.96 x 1.0
2
.05 x 3.0
=1.96
.15
2
13.06
2
=
171≈
QM for WINDOWSQM for WINDOWS
Sample SizeDetermination
Direct Time StudyDirect Time Study
ADDITIONAL COMMENTS
When observed times are not consistent, they need to be reviewed. Abnormally short or long times may be the result of an observational error and are usually discarded.
Normal times (NT) are sometimes computed for each element of a job because the performance rating may vary for each element. In other words, the same worker may be fast on some tasks but slow or average on other tasks.
Intra - Job Performance RatingsIntra - Job Performance Ratings
EXAMPLE
Job Element Performance Rating
Drawing Materials 0.99
Assembling Parts 1.08
Product Coating 0.83
Product Inspection 1.20
A MUCH MORE ACCURATESTANDARD SETTING
PROCEDURE !
Predetermined Time StandardsPredetermined Time Standards
• Routine, repetitive jobs are divided into basic motions
of the human body.
• These motions have been studied under numerous conditions and assigned specific times.
• A time standard for a particular job is found by adding these basic motion times together.
Predetermined Time StandardsPredetermined Time StandardsTHERBLIGS
Basic or elemental motions of the human body are called therbligs
Term was coined by Frank Gilbreth
They include such activities as select, grasp, position, assemble, reach, hold, and inspect
Time values for therbligs are specified in very detailed tables
*
GILBRETH SPELLED BACKWARDS WITH “T” AND “H” TRANSPOSED
Predetermined Time StandardsPredetermined Time StandardsTHERBLIGS: ELEMENTAL MOTIONS OF THE HUMAN BODY
KNEESKNEES
HEADHEAD
ARMSARMS
TORSOTORSO
LEGSLEGS
ELBOWSELBOWS
FEETFEET
ONE OF THE FIRST JOBS STUDIED WAS THAT OF THE STOKERONE OF THE FIRST JOBS STUDIED WAS THAT OF THE STOKER
Frank & Lillian Gilbreth Colleagues of Frederick Taylor
Among the first to systematically seek the best way to perform jobs
They used clocks, still cameras, and movie cameras to record the movements of workers while they performed their jobs
Their family was the basis for the movie “Cheaper by the Dozen”.
1950&
1995
The Gilbreth Family
PHOTOGRAPH TAKEN AT THEIR MONTCLAIR, NEW JERSEY HOMEPHOTOGRAPH TAKEN AT THEIR MONTCLAIR, NEW JERSEY HOME
Predetermined Time StandardsPredetermined Time StandardsTHERBLIG TIME MEASUREMENT
Stated in terms of time measurement units or TMUs
One TMU equals .00001 hours
One TMU equals .0006 minutes
There are 100,000 TMUs in one hour
Predetermined Time StandardsPredetermined Time Standards
• Methods Time Measurement is a product of the MTM
Association, Fairlawn, New Jersey 07410.
• It is a family of products including MTM-C which deals with clerical tasks, and MTM-HC which deals with healthcare industry tasks.
• Provides a comprehensive system of predetermined time standards which would be prohibitively expensive for a single firm to develop.
• Services include consulting, data base rental, and custom performance standards for one or more jobs set by MTM professional staff.
MTM ASSOCIATION
MTM IS A COPYRIGHTED PRODUCT
Predetermined Time StudyPredetermined Time StudyUSING THE MTM SYSTEM TO DEVELOP A TIME
The most complex motion or therbligin the MTM system is get and place .
We must know four things:
1. What is to be gotten.2. Its approximate weight.3. Where it must be placed.4. How far it must be moved.
Predetermined Time StudyPredetermined Time StudyDEVELOPING A TIME FOR GET AND PLACE
The conditions for getting a unit and placing it before the worker are:
1. A part is needed for assembly.2. Its weight is less than 2 pounds.3. It must be moved to the worker’s immediate front.4. It must be moved between 8 and 20 inches from the far corner of a work table.
Predetermined Time Study
Each Part
< 2 lbs
WorkBench
StandingWorker
8 t
o 2
0 in
ches
8 to
20
inch
es
“ GET AND PLACE ” EXAMPLE
Predetermined Time StudyPredetermined Time StudySAMPLE MTM TABLE FOR “GET” AND “PLACE”
DistanceDistanceIn In
InchesInches< 8< 8 > 8> 8
< 20< 20> 20> 20< 32< 32
WeightWeight ( lbs. )( lbs. )
“ GET ” Conditions
“ “ PLACE ”PLACE ”AccuracyAccuracy
Code 1 2 3
Approx AA 20 35 50
<2 lbs.<2 lbs. EASY LooseLoose AB 30 45 60
TightTight AC 40 55 70
THEREFORE MTM TIME FOR THIS THERBLIG IS 35 TMUs AND ITS CODE No. IS AA2
PredeterminPredetermined Time Studyed Time StudyDEVELOPING A TIME FOR GET AND PLACE
Additional Weight Categories ( not shown )
> 2 pounds < 18 pounds
> 18 pounds < 45 pounds
Additional Conditions of “Get” ( not shown )
Difficult
Handful
OF COURSE THE MTM THERBLIGS FOR THESE CONDITIONS WOULD HAVE DIFFERENT CODES SUCH AS AD2, AE3
Predetermined Time StudyPredetermined Time StudyCOMPLETE MTM JOB TIME EXAMPLE
JOB ELEMENT( THERBLIG )
JOB ELEMENT
CODE
JOB ELEMENT TIME( in TMUs )
Draw item “A” from left corner of table
35
Draw item “B” from
right corner of table55
45
83
40
∑ TMUs 258
Assemble the two Items
Inspect the assembly
Place the assemblyin a box
AA2
AC2
AD2
PT1
GB3
.0006 x 258 = .1548 STANDARD MINUTES FOR THIS COMPLETE JOB
Predetermined Time StudyPredetermined Time Study2nd EXAMPLE
Suppose there are 8 therbligs in a short-cycle, repetitive job
Suppose the sum of the therblig TMUs = 397.9
Since each TMU = .036 seconds, this job’s cycle time equals 14.32 seconds ( 397.9 x .036 )
14.32 seconds = .23838 minutes ( 14.32 / 60 )
251.7 cycles of this job should be expected each hour by management ( 60 / .23838 )
Standard hourly output would therefore be 252 units
Predetermined Time StudyPredetermined Time Study
Does not disrupt the actual production operation.
No performance ratings are necessary.
No allowance factors are necessary.
Unions tend to accept it as fair.
Particularly effective in firms that employ many workers performing similar tasks, i.e.
it is cost-effective.
Can be used for planning purposes because the time standard can be set before the job actually exists!
ADVANTAGES
Work SamplingWork Sampling
o Developed in England in the 1930s by Leonard Tippet
o Estimates the percentage of time that a worker spends on various tasks.
o Random observations are used to record employee activity.
o The only technique available for measuring and evaluating non-repetitive jobs.
The Most UsedThe Most UsedTechnique in theTechnique in theService SectorService Sector
Leonard Henry Caleb TippettLeonard Henry Caleb Tippett1902 - 19851902 - 1985
English physicist and statisticianwho used what he called a
“snap reading method” to obtain,at random time intervals, observations
of textile machine operators forthe purpose of estimating the
percentage of time spent on theirduties.
L.H.C. Tippett
Leonard Henry Caleb TippettLeonard Henry Caleb Tippett
Awarded the Walter Shewart Medal of the American Society for Quality Control
Awarded the Warner Medal of the Textile Institute for improving the production efficiency and operative utilization of the textile industry
Educated at Imperial College, and University College, London
President of the Royal Statistical Society, 1965
Shirley Institute, Manchester, England, 1925-1965
1902 - 1985
Work Sampling ApplicationsWork Sampling Applications
Establishing labor and production standards.
Discovering how employees allocate their time for both work and non-work activity.
Providing the basis for staffing changes, job training, reassignments of duties, hiring, and termination.
Work Sampling In ActionWork Sampling In Action
The mail order catalogerLand’s End expects its
call center representativesto be busy 85% of the time
When the “busy” ratio hits90% , the firm believes it is
not attaining its set goalof high quality service
The firm then plansto hire more
representativesto restore the desired
level of service
Work SamplingWork Sampling
Monday 10:30 am Flying paper airplanes
Wednesday 2:20 pm Watching TV
Thursday 9:45 am Reading Sports Page
Thursday 1:25 pm Buying Cruise Tickets On-Line
Friday 2:30 pm Doing Homework for Night School
Friday 4:30 pm Left Early
SIX RANDOM VISITS TO JOE’S OFFICE
JOEJOE
BOSSBOSS
EXPECT TOSEE THIS
ANDMORE !
Work Sampling ProcedureWork Sampling Procedure
I. Take a preliminary sample to obtain an estimate of a parameter value such as the percentage of time a worker is busy.
II. Compute the sample size required for the formal work sampling study.
III. Prepare a worker observation schedule.
IV. Observe and record worker activities.
V. Determine how workers are spending their time.
Work Sampling ExampleWork Sampling ExampleThe REGISTRY
of MOTOR VEHICLES
The manager of a branch officeestimates that her employeesare idle 25% of the time. Shewants to confirm or disprove this by taking a work sample
that is accurate to within +/- 3% and yields a 95% confidence
Sample SizeSample Size CoComputation Formulamputation Formula
z x p x q2
ε 2
where:
n = required sample size
z = standard normal deviate for the desired confidence level
p = estimated value of the sample proportion ( of time worker is “busy” )
q = estimated value of the sample proportion ( of time worker is “idle” )
ε = acceptable error level ( in percent )
n =
Sample Size ComputationSample Size Computation
n = (2) x (.25)(.75)
(.03)= 833
2
2
95% CONFIDENCE LEVEL ( z ) 3 PERCENT TOLERATED ERROR ( ε )
75% BUSY PROPORTION ( q )25% IDLE PROPORTION ( p )
WORK SAMPLING
WE COULD HAVE DESIGNATED THE “BUSY” PROPORTION “p” AND THE “IDLE” PROPORTION “q”
Work Sampling ExampleWork Sampling ExampleThe REGISTRY
of MOTOR VEHICLES
Utilizing the sample size formula,she finds that 833 observations
should be taken. If the percentageof idle time observed is not closeto 25% as the study progresses,the number of observations may
need to be recomputed and raisedas appropriate.
QM for WINDOWSQM for WINDOWS
Work SamplingWork Sampling
Work Sampling ResultsWork Sampling ResultsThe REGISTRY of MOTOR VEHICLES
Number of Observations Activity
485 on phone / meeting clients
126 idle
62 personal time
23 supervisor meetings
137 filing, data entry
∑ = 833NOT
WORKRELATED
Work Sampling ConclusionWork Sampling ConclusionThe REGISTRY of MOTOR VEHICLES
All but 188 of the observations are work-related.
Since 22.6% is less idle time than the branch manager believes necessary to ensure a high client service level, she needs to find a way to reduce current work loads.
This could be accomplished via a reassignment of duties or the hiring of additional personnel.
( 126 IDLE & 62 PERSONAL )
( 188 / 833 = 22% )
Employee Observation ScheduleEmployee Observation SchedulePREPARATION
EXAMPLE
Draw five random numbers from a table:
07 12 22 25 49
These random numbers can then be usedto create an observation schedule:
9:07 9:12 9:22 9:25 9:49
RANDOM NUMBERS ARE USED TO GENERATE THE VISITATION SCHEDULE
9:07 - JOE
9:12 - BOB
9:22 - CAROL
9:25 - TIM
9:49 - JOAN
Employee Observation ScheduleEmployee Observation Schedule
COMMENTS
Observations are to be made in a non-intrusive manner so as not to distort employee normal work patterns.
Observations are to be made in a random and unbiased manner over a period of 2 weeks in order to ensure a valid sample.
Activities that constitute “work” must be clearly defined such as filing, data entry, meetings, and writing reports.
Work Sampling ResultsWork Sampling ResultsTYPICAL MANUFACTURING SITUATION
PRODUCTIVE WORK………………………75%IDLE TIME BETWEEN TASKS……………..9%BREAKS AND LUNCH………………………7%DOWNTIME & UNSCHEDULED TASKS….4%CLEANUP…………………………………......3%START- UP…………………………………….2%
Work SamplingWork Sampling
• LESS EXPENSIVE
• NO TIMING DEVICES
• LITTLE TRAINING NEEDED
• STUDY CAN BE DELAYED TEMPORARILY WITH LITTLE IMPACT ON THE RESULTS
• WORKER HAS LITTLE CHANCE OF AFFECTING THE OUTCOME
• LESS LIKELY TO GENERATE EMPLOYEE OBJECTIONS
ADVANTAGES
Work SamplingWork Sampling
• IT DOES NOT DIVIDE WORK ELEMENTS (THERBLIGS) AS THOROUGHLY AS FORMAL TIME STUDIES
• IT CAN YIELD INCORRECT / BIASED RESULTS IF THE OBSERVER DOES NOT CONFORM TO RANDOM ROUTES OF TRAVEL AND RANDOM OBSERVATION
• IT TENDS TO BE LESS ACCURATE WHEN CYCLE TIMES ARE SHORT
DISADVANTAGES
Work Measurement & Standards
Applied Management Science for Decision Making, 1e Applied Management Science for Decision Making, 1e © 2011 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD© 2011 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD