Estimating defects in commercial software during operational use

A new model that accounts for the usage growth of commercial software during the operational phase, and that incorporates a factor to estimate (from field-failure reports) the usage growth is presented. The model can estimate the number of remaining unique defects in wide-distribution commercial software during the operational phase, and the anticipated arrival times of customer-reported failures attributable to these unique defects. The model is based on the Weibull distribution, which assumes that field usage of commercial software increases as a power function of time. The model was fit to the actual failure times for two commercial software products-one that runs on 10⁵ systems, and the other that runs on 10⁴ systems. The model fits the general shape of the arrival distribution for the actual defect discovery times, but there are minor peaks in the example data that are not explained by the model. Some of the minor modes correspond to peak defect discovery times for subsequent releases of the software