The effect of the number of inspectors on the defect estimates produced by capture-recapture models

Inspections can be made more cost-effective by using capture-recapture methods to estimate post-inspection defects. Previous capture-recapture studies of inspections used relatively small data sets compared with those used in biology and wildlife research (the origin of the models). A common belief is that capture-recapture models underestimate the number of defects but their performance can be improved with data from more inspectors. This increase has not been evaluated in detail. This paper evaluates new estimators from biology not been previously applied to inspections. Using a data from seventy-three inspectors, we analyze the effect of the number of inspectors on the quality of estimates. Contrary to previous findings indicating that Jackknife is the best estimator, our results show that the SC estimators are better suited to software inspections. Our results also provide a detailed analysis of the number of inspectors necessary to obtain estimates within 5% to 20% of the actual.