Definition

The Mean Age of Unresolved Defects is a measure of how long the registered defects stay unresolved. To give the full picture of the situation, Mean Age of Unresolved Defects should be tracked along with Mean Time to Fix.

Calculation

To be able to calculate that metric, it is important that in your defect tracking system you track:

• defect registration date and time
• defect status

Mean Age of Unresolved Defects = ((Current date & time of unresolved defect #1 - registration date & time unresolved defect #1) + ... +  (Current date & time of unresolved defect #N - registration date & time of unresolved defect #N)) / total number of unresolved defects

Dimensions

It should be possible to monitor Mean Age of Open Defects in following dimensions:

• product/project
• priority

Presentation

Good visualization could be a set of 2 charts: a bar chart with current values for each priority and a line chart with historical trend of the metric over all priorities. 

For Mean Age of Unresolved Defects it is important to track the trend of the values. In most cases it makes sense to constantly reduce average age, which indicates that you are fixing the defects.

Example

Today is September 22, 2010, local time 16:08. For simplicity's sake, we can suppose there are currently just three open defects in the project:

	Defect 1	Defect 2	Defect 3
Registration date & time	02.09.2010 09:41:29	17.08.2010 14:58:01	11.08.2010 10:31:14
defect status	Open / Unresolved	Open / Unresolved	Open / Unresolved

Mean Age of Unresolved Defects = ((22.09.2010 16:08 - 02.09.2010 09:41) + (22.09.2010 16:08 - 17.08.2010 14:58) + (22.09.2010 16:08 - 11.08.2010 10:31)) / 3 = 

(20 d 6 h 27 min + 36 d 1 h 10 min + 42 d 5 h 37 min) / 3 = 98 d 13 h 14 min / 3 ~ 32 d 20 h 25 min