Inspection Defect Missed Prediction Minimum Process Requirements J.K. Orr 2015-07-27

Copyright 2015 By James K. Orr 1

Minimum Process Requirements To Predict Defects Missed

In A Series Of Software Inspections

James K. OrrIndependent Consultant

[email protected]


Objective

• Provide as accurate as possible estimate of defects remaining after a series of software inspections (for example, all inspections on an upcoming release) based on the minimum amount of additional process activity and information collected from the inspection meeting.


ContentsSection Page

Application Of Process Example 5Prediction Charts For 100 and 200 Defects Found 10Tables And Plots To Compute Number Of Defects Found And Confidence Limits

13

Simulation Basis Inspection Team Effectiveness As A Function Of Capture – Recapture Metric

19

Simulation Basis For Number Of Defects Found And Confidence Limits

23

Conclusions 27


Application Of ProcessExample


Additional Inspection Process Steps

• Additional Step At Start Of Inspection– Moderator asks each inspector how many defects were found

prior to meeting and temporarily records information for use at end of meeting.

• Additional Step At End Of Inspection (Moderator has previously determined how many valid defects were found).– For each valid defect, the Moderator asks inspectors to indicate if

they found the defect prior to the inspection meeting. Moderator insures data from each inspector is consistent with information from the start of meeting.

• Moderator provides a coordinator with the information collected in the format on the following page.


Additional Information Collected Inspection

Identification Information

Defects Found Pre-Inspection By Only

One Inspector

Defects Found Pre-Inspection By Two

Or More Inspectors

Additional Defects Found During The

MeetingInspection 105 3 1 0


Additional Metrics Coordinator Process

• A metric is computed for use in a chart or table lookup.– Capture-Recapture Metric = (Sum Of Errors Found

By Two Or More Inspectors) / (Sum Of Errors Found By Only One Inspector)

• Lookup Predicted Defects Missed By Multiple Inspections Based On Total Number Of Errors Found and Capture-Recapture Metric


Metrics Coordinator CalculationInspection

Identification Information

Defects Found Pre-Inspection By Only

One Inspector

Defects Found Pre-Inspection By Two

Or More Inspectors

Additional Defects Found During The

MeetingInspection 105 3 1 0

Inspection 106 3 1 0





Sum 17 8 1

Calculate Capture-Recapture Metric

Value Of Capture-Recapture Metric

Predicted Defects Missed By Multiple Inspections

= 8 / 17 47.06 %For 25 Errors Found

18See Next Page


Prediction Of Defects RemainingTotal Of 25 Defects Found


Prediction Charts For 100 and 200 Defects Found






Tables And Plots To Compute Number Of Defects Found And

Confidence Limits


Table Of Factor Based On Capture – Recapture Metric


Plot Of Factor Based On Capture – Recapture Metric


Table Of Factor Based On Number Of Defects Found


Plot Of Factor Based On Number Of Defects Found


Sample CalculationCalculate Capture-

Recapture Metric

Value Of Capture-

Recapture Metric

Uncorrected Defects Missed

Divided By

Defect Found In

Inspection

Number Of Defects

Found In Inspection

Adjusted Expected

Value Factor

Number Of Defects Missed

In Inspection

= 8 / 17 47.06 % 0.656Calculated, Not From

Table

25 109% = integer (25 * 0.656 *1.09)

=integer( 17.9)= 18

• Note: Detain analysis done for 25, 100, and 200 defects found in inspections.

• Values in Table are interpolated for intermediate values.


Simulation BasisInspection Team Effectiveness

As A Function Of Capture – Recapture Metric


Team Inspection Effectiveness As A Function Of Capture – Recapture Metric


Simulation To Develop One Data Point On Prior Chart


Convert To Missed Defects

DefectsMissed

=DefectsFound *

1 - 1( )_______________Verification Effectiveness


Simulation Basis For Number Of Defects Found

And Confidence Limits


Prediction Error Analysis 25 Defects Found

Legend:Insp 4 Eff 20 %Means SimulationWith 4 Inspectors Each with Individual Defect Detection of 20 % Of Errors In Inspected Product



Legend:Insp 6 Eff 15 %Means SimulationWith 6 Inspectors Each with Individual Defect Detection of 15 % Of Errors In Inspected Product



Legend:Insp 4 Eff 20% to 25 %Means SimulationWith 4 Inspectors Each with Individual Defect Detection of Random From 20 % to 25 % Of Errors In Inspected Product


Conclusions

• A detail, simple method has been presented which will allow a project to perform prediction of defects missed in a series of software inspections with minimum effort.

• For projects with minimal software metric experience, useful data can be produced with very minor effort.

• For projects with extensive software metric experience, the project can begin to evaluate usefulness of capture-recapture metrics with minimum resistance due to collection of project data without individual inspector information (used by moderator in the inspection team meeting only).

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Inspection Defect Missed Prediction Minimum Process Requirements J.K. Orr 2015-07-27

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