Escaped Defects Found

Definition

An escaped defects is a defect that was not found by, or one that escaped from, the quality assurance team. Typically, those issues are found by end users after released version has made available to them. The metrics Escaped Defects Found counts number of new escaped defects found over period of time (day, week, month).
Calculation
To be able to calculate that metric, it is important that in your defect tracking system you track:

* affected version, version of software in which this defect was found.
* release date, date when version was released

The calculation process:

* Find all versions that were already released
* for each version, find all defects that affected the version
* if defect creation date is after version release date then this defect is an escaped defect.
* now count all those escaped defects.

Dimensions
It should be possible to monitor Escaped Defects Found in following dimensions:

* Affected version, to monitori metric value of any released version.
* Project/Product. To aggregated Escaped Defects Found over all released versions of the project or product.

Usage
I like this metric because tracking that sends correct message to development team: functionality that is released, should be of good quality. Less Escaped Defects almost always means good job of QA team.

Also important reason to keep the number of Escaped Defects low, is that fixing a single escaped software defect can take from a week to several weeks of effort to correct. As you have to include the time to isolate, repair, checkout, retest, reconfigure and redistribute. Fixing defect inside the development iteration is always much cheaper.
Presentation
Best presentation is a simple bar chart, where each bar shows number of escaped defects found per (day/week/month/quarter/year). Depending on your requirements you may want to create this chart for a whole company or each product. Also to compare quality of different versions it could makes sense to show bar chart with current values of escaped defects for each version of the product.