(Let it be known: this is an example to be used in testing classes and exercises. It is not something that I use or advocate. However, it is taken verbatim from an old client document.)
DER – Defect Escape Rate
The Defect Escape Rate measures the number of undiscovered defects that escaped detection in the product development cycle and were released to customers. An escape is a defect found while using a released product. DER is defined as:
DER = (Defect Escapes /Total Defects)∗100
DER is a lagging indicator of product quality. The number of escapes is always zero until after the product is released. It is reported as a percentage and a low number is desired. Each business unit has a target DER percentage and an Escape Analysis should be performed on each defect to improve test coverage. It is desirable for the DER for a product line to decline over time.
To calculate DER:
- Compute the total defects found in this product version by noting the number of defects returned by querying for
Product (current product name)
Found in Version (all “found in” versions associated with the current product version)
Fixed in Milestone (none; for this query any “fixed in: milestone” is included)
Status (none; for this query every status is included)
Resolution ( — OR Fixed OR Moved OR Feature OR WontFix)
Severity ( Critical OR Major OR Normal OR Minor )
Only bugs changed between (<blank> and <blank> where one or more of the following changed: <none>) - Compute escapes by noting the number of defects returned by the following query:
Product (current product name)
Found in Version (all “found in” versions associated with the current product version)
Fixed in Milestone (none; for this query any “fixed in: milestone” is included)
Status (none; for this query every status is included)
Resolution ( — OR Fixed OR Moved OR Feature OR WontFix)
Severity ( Critical OR Major OR Normal OR Minor )
Only bugs changed between (<First Customer Ship of (Current Product Version – 1) > and <First Customer Ship of Current Product Version + 1 Year> where one or more of the following changed: [Bug_creation]) - Use the following formula to calculate DER:
DER = escapes / TotalBugs
As an exercise: what problems can you see here? How might this calculation of “defect escape ratio” be wrong or misleading?