Time Between Escaped Defects

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Definition

The Time Between Escaped Defects is a metric that shows how often new defects are identified in released versions of the product.

Calculation

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

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

Ideally, defects are registered to different components so you can compare the value of this metric for different components.

The manual calculation of this metric is complicated, but an excel can help:

1. Filter out all escaped defects from your bug tracker. If you are interested in this metrics for specific period then filter out only escaped defects registered during this period.

2. Sort all defects by registration time.

3. If you are using excel, create a new formula column that would calculate time between defect registration time and previous defect registration time.

4. When you have a table of values for Time Between Defects, you can do basic statistics like: calculate mean, min, max, ..

Dimensions
It should be possible to monitor Time Between Escaped Defects in following dimensions:
product/project
affected version
priority
Presentation
There should preferably be 2 charts to watch the Time Between Escaped Defects:
a bar chart with Mean Time Between Escaped Defects for different components or products that your are working on. If you don’t have multiple products, then try to gather statistics from other companies or teams that develop similar complexity products.
a trend line chart to make sure the gap between new defects are found is increasing.

Encyclopedia of Software Development Life Cycle Metrics