Estimating the Number of Remaining Defects after Inspection

An essential component of all software inspection processes is a well-founded decision about continuing or stopping the current process. This decision should be based upon directly relevant quantitative information – the number of defects remaining in the artefact. This quantity can be estimated by the use of capturerecapture methods. Several Software Engineering papers have explored this topic, but the questions: how applicable is this approach, and which capture-recapture technique is best, still remain unresolved. This paper attempts to shed further light upon these questions. After reviewing, the relevant capture-recapture models and the attempts at evaluating them within a Software Engineering context, the paper proceeds to evaluate the models by using data collected from subject-based experiments on software inspection. The experiments used artefacts where the number of defects are known and hence the paper produces a direct measure of the accuracy of the various capture-recapture techniques. The paper reports that the heterogeneity models are, in general, better especially the Jackknife estimator. But also reports that further work is required, to correct the limitations of the current models, if reliable estimates are to be achieved.