Software Economics Phase Yield Emerson Murphy-Hill Creative Commons Attribution 4.0 License. Material Created by NCSU Software Engineering Faculty.

Fault removal yield Phase yield = removed in phase removed in phase + escapes from phase Phases: design review, code, code review, compile, test Phase escapes: defects injected before or during the phase, not found before or during the phase, and found later The “escapes from phase” measure cannot be precisely calculated until after the program has been used in the field (need post-development defects) – need 20/20 hindsight even then some failures can surface for years

Fault Removal Yield Example Phase Injected Removed Cumulative Injected Cumulative Removed Requirements 1 Design 5 6 Design Review 3 Code 15 21 4 Code Review 8 12 Static Analysis 18 Test Field Total 26 Note: the faults show up in the “injected” column if they were analyzed and removed prior to release. Design Review Yield = 3/(0+6) = 50% Code Review Yield= 8/(8+9) = 47% Process Yield = 21/26 = 81%

Quality Assurance Filters - Examples 100 errors Inspection (50%) 50 errors Testing (50%) 25 errors To customer Solo programming with inspection Testing To customer Testing (50%) Solo programming without inspection or pair programming Pair Programming Paired team without inspection See course pack page 23