BIs exposed to a sterilant that results in a quantal-zone outcome demonstrate more variability than unexposed BIs but also show a low frequency of BIs with a prolonged grow-out time. The MIT method proposed in this paper using the CST sterilization exposure takes into account this increased variability but properly avoids the occurrence and inappropriate influence of “outlier” results. In contrast, an unforeseen consequence of the 30-80% survival window of the FDA CDRH protocol is that the RIT is driven by the outlier results of large percentages of BIs having only a single spore. This effect can be seen in the fact that a shorter incubation time can be achieved if the average nonsterile results are closer to 80% versus 30%, which is a result attributed to the difference in the fraction of nonsterile BIs having only a single surviving spore. This consequence is clearly undesirable for a test method and demonstrates a lack of robustness and reproducibility.