Anna University, Final CSE, Software Quality Management

1. Defect Removal Effectiveness
Defect Removal Effectiveness
Software Quality Management
Software Quality Management
Unit 3
G. Roy Antony Arnold
G R A A ld
Asst. Professor / CSE
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2. • Defect removal i one of the top expenses i
f l is f h in
any software project and it greatly affects
schedules.
• Effective defect removal can lead to
reductions in the development cycle time and
g
good product quality.
p q y
• It is important for all development
organizations to measure the effectiveness of
their defect removal processes.
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3. • Fagan (1976) defined error detection efficiency as:
Errors found by an Inspection
X 100%
Total errors in the product before inspection
• Jones's definition (1986), stated here, is very similar to Fagan's:
– Removal Efficiency = Defects found by removal operation
y p
X 100%
Defects present at removal operation
Defects found
X 100%
Defects found + Defects not found (found later)
• IBM Houston received the first NASA Excellence Award for Quality
and Productivity in 1987
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4. • One of the four metrics IBM used to manage quality is
One of the four metrics IBM used to manage quality is
the early detection percentage, which is actually
inspection defect removal effectiveness
Early Detection Percentage =
Number of major inspection errors
Number of major inspection errors
X 100%
Total number of errors
• where total number of errors is the sum of major
inspection errors and valid discrepancy reports
(discrepancy report is the mechanism for tracking test
(di t i th h i f t ki t t
defects).
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6. • The effectiveness measure by Dunn (1987) differs little from
The effectiveness measure by Dunn (1987) differs little from
Fagan's and from Jones's second definition.
• Dunn‘s definition is:
Effectiveness of activity (development phase ) =
Number of defects found by activity
Number of defects found by activity
X 100%
Number of defects found by subsequent activities
• This metric can be tuned by selecting only defects present at
the time of the activity and susceptible to detection by the
y p y
activity.
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7. • Daskalantonakis (1992) describes the metrics used at Motorola for
software development.
software development
Total Defect Containment Effectiveness (TDCE) =
Number of pre‐release defects
Number of pre‐release defects
Number of pre‐release defects + Number of post‐release defects
Phase Containment Effectiveness (PCEi) =
Number of Phase i errors
Number of Phase i errors + Number of phase i defects
• Where phase i errors are problems found during that development
Where phase i errors are problems found during that development
phase in which they were introduced, and
• Phase i defects are problems found later than the development
phase in which they were introduced.
phase in which they were introduced.
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8. Defects removed (at the step)
( )
X 100%
Defects existing on step entry + Defects injected during development of the step
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10. • B d on a special study commissioned b th D
Based i l t d i i d by the Department
t t
of Defence, Jones estimates the defect removal
effectiveness for organizations at different levels of the
development process capability maturity model ( (CMM):)
– Level 1: 85%
– Level 2: 89%
– Level 3: 91%
– Level 4: 93%
– Level 5: 95%
l
• These values can be used as comparison baselines for
organizations to evaluate their relative capability with
regard to this important parameter.
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11. • Based on historical and recent data from three
software engineering organizations at General
Dynamics Decision Systems, Diaz and King (2002)
report that the phase containment effectiveness by
CMM level as follows:
– Level 2: 25.5%
– Level 3: 41.5%
– Level 4: 62.3%
– Level 5: 87.3%
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12. Phase Inserted
Phase Inserted Cumulative % of Defects
Cumulative % of Defects
removed through Acceptance
Test
Requirements 94%
Top Level Design
Top‐Level Design 95%
Detailed Design 96%
Code and Unit
Code and Unit Test 94%
Integration Test 75%
System Test
System Test 70%
Acceptance Test 70%
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