Quick reference – Defect Injection & detection

 Defect injection is equal to No of defect created in development effort(developer total hrs spent).

 Defect detection is “confirmed defects detected” in defined  period of time.

 Defect discovery(detection) rate is equal to no. of defects found in testing effort (Tester total hrs spent)

 Defect Density = No. of bugs / Developer effort (not tester)

 Bug Density = Defects in Releases / Total Story Points
(Where “Story Points” are complexity points, Nebulous Units of Time, (NUTs)), or Pair Hours.

 **Defect Removal Effectiveness = Defects Removed (at the step)/ Defects existing on step entry )+ defects injected during the step x 100%

 Industry Average: “about 15 – 50 errors per 1000 lines of delivered code” (refer: The book “Code Complete” by Steve McConnell)

Industry Derived Measures from ISBSG [http://www.isbsg.org]


500–8500 FP/FTE, median 1600

10–1200 KLOC/FTE, median 300


2–60 defects /1000FP, median 9.3, mean 16

.01–.95 defects/KLOC, median .02, mean .18

Median 15 hours/defect Proportions


2% extreme, 13% major, 85% minor

Other References:





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