Defect Age Metrics

Defect Age can be measured in terms of any of the following:

• Time
• Phases

DEFECT AGE (IN TIME)
Definition
Defect Age (in Time) is the difference in time between the date a defect is detected and the current date (if the defect is still open) or the date the defect was fixed (if the defect is already fixed).
Elaboration

• The ‘defects’ are confirmed and assigned (not just reported).
• Dropped defects are not counted.
• The difference in time can be calculated in hours or in days.
• ‘fixed’ means that the defect is verified and closed; not just ‘completed’ by the developer.

Defect Age Formula

Defect Age in Time = Defect Fix Date (OR Current Date) – Defect Detection Date

Normally, average age of all defects is calculated.
Example
If a defect was detected on 01/01/2009 10:00:00 AM and closed on 01/04/2009 12:00:00 PM, the Defect Age is 74 hours. Uses

• For determining the responsiveness of the development/testing team. Lesser the age better the responsiveness.

DEFECT AGE (IN PHASES)
Definition
Defect Age (in Phases) is the difference in phases between the defect injection phase and the defect detection phase.
Elaboration

• ‘defect injection phase’ is the phase in the software life cycle where the defect was introduced.
• ‘defect detection phase’ is the phase in the software life cycle where the defect was identified.

Defect Age Formula

Defect Age in Phase = Defect Detection Phase – Defect Injection Phase

Normally, average of all defects is calculated.
Example
Let’s say the software life cycle has the following phases:

1. Requirements Development
2. High-Level Design
3. Detail Design
4. Coding
5. Unit Testing
6. Integration Testing
7. System Testing
8. Acceptance Testing

If a defect is identified in System Testing and the defect was introduced in Requirements Development, the Defect Age is 6.
Uses

• For assessing the effectiveness of each phase and any review/testing activities. Lesser the age better the effectiveness.