1. Model for Quantative Defect Removal
Source: Galin, D., ‘Software Quality Assurance’. Addison Wesley, 2004.

2. Analogie – Traitement des eaux usées
Eau prélevée du St-Laurent !
Mesure
Eau après premier traitement
Mesure
Mesure
Eau après x traitements
Filtres
Mesure
Eau potable
Qualité connue et risque connu
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3. Defect removal effectiveness and cost
Software development phase
Average % of defects originating in phase
Average relative defect removal cost
Requirement specification
Design
Unit coding
Integration coding
Documentation
System testing
Operation
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4. Defect removal effectiveness and cost
Software development phase
Average % of defects originating in phase
Average relative defect removal cost
Requirement specification
15%
Design
35%
Unit coding
30%
Integration coding
10%
Documentation
System testing
50%
Operation
100%
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5. Defect removal effectiveness and cost
Software development phase
Average % of defects originating in phase
Average relative defect removal cost
Requirement specification
15% 1
Design
35%
2.5
Unit coding
30%
6.5
Integration coding
10% 16
Documentation 40
System testing
50%
Operation
100%
110
Boehm
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6. Defect removal effectiveness
Quality assurance activity
Defects removal effectiveness
Specification requirement review
50%
Design inspection
70%
Design review
Code inspection
Unit test
Integration tests
Documentation review
System test
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7. Defect removal effectiveness and cost
· POD = Phase Originated Defects
· PD = Passed Defects (from former phase or former quality assurance activity)
· % FE = % of Filtering Effectiveness (also termed % screening effectiveness)
· RD = Removed Defects
· CDR = Cost of Defect Removal
· TRC = Total Removal Cost = RD x CDR.
Note: Percentage of removed defect is less than % of detected defects since 10-17% of defect correction are inadequate.
7/24/2019

8. Defect removal effectiveness and cost
· POD = Phase Originated Defects
· PD = Passed Defects (from former phase or former quality assurance activity)
· %FE = % of Filtering Effectiveness (also termed % screening effectiveness)
· RD = Removed Defects
· CDR = Cost of Defect Removal
· TRC = Total Removal Cost. TRC = RD x CDR.
7/24/2019

9. Defect removal effectiveness and cost
· POD = Phase Originated Defects
· PD = Passed Defects
· %FE = % of Filtering Effectiveness
· RD = Removed Defects
· CDR = Cost of Defect Removal
· TRC = Total Removal Cost.
= RD x CDR.
7/24/2019

10. Defect removal effectiveness and cost with inspection
Quality assurance activity
Defects removal effectiveness for standard SQA plan
Defects removal effectiveness for comprehensive SQA plan
Specification requirement review
50%
60%
Design inspection
-----
70%
Design review
Code inspection
Unit test
40%
Integration tests
Documentation review
System test
Operation phase detection
100%
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11. Defect removal effectiveness and cost with inspection
System tests
RD = 4
CDR = 40
2.6
TRC = 160 cu
Operation
POD = 0
PD = 2.6
% FE = 100
RD = 2.6
· POD = Phase Originated Defects
· PD = Passed Defects
· %FE = % of Filtering Effectiveness
· RD = Removed Defects
· CDR = Cost of Defect Removal
· TRC = Total Removal Cost.
= RD x CDR.
CDR = 110
TRC = 286 cu
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12. Comparisons Less costly to maintain (296 instead of 759)
Less defects when shipped for operation (2.6 vs. 6.9)
Economy of 41% counting additional internal QA activities
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