Monday, May 11, 2009

Defect Removal Efficiency...

(From Systematic software testing By Rick David Craig, Stefan P. Jaskiel): Ref: Google Books...

A measure of the number of defects discovered in an activity versus the number that could have been found. Often used as a measure of testing effectiveness.

Defect Removal Efficiency (DRE) is a measure of the efficacy of your SQA activities.. For eg. If the DRE is low during analysis and design, it means you should spend time improving the way you conduct formal technical reviews.

DRE = E / ( E + D )

Where E = No. of Errors found before delivery of the software and D = No. of Errors found after delivery of the software.

Ideal value of DRE should be 1 which means no defects found. If you score low on DRE it means to say you need to re-look at your existing process. In essence DRE is a indicator of the filtering ability of quality control and quality assurance activity . It encourages the team to find as many defects before they are passed to the next activity stage. Some of the Metrics are listed out here:
DRE doesnt measure EFFICIENCY. It can be better called DEFECT DETECTION PERCENTAGE

DRE = (Number of bugs found in testing / number of bugs found in testing + number of bugs not found)*100
Number of bugs found in testing = 80 + 40 + 100 + 20 + 50 + 30 = 320
DRE = 320 / [320+30]*100 = 0.91*100 = 91%

NOTE: DRE is also sometimes used as a way to measure the effectiveness of a particular level of test. For example, the system test manager may want to know what the DRE is for system testing. The number of bugs found in system testing should be placed in the numerator, while those same bugs plus the acceptance test and production bugs should be used in the denominator. See the example below: (consider the same example as above)

System test DRE = # of bugs found in system testing / [# of bugs found in ST + # of bugs found in AT and Production]*100

System test DRE = (50/[50+30+30])*100 = 45.45%