by Robert J. Seely, Amgen, Inc. Louis Munyakazi, John Haury, Heather Simmerman, W. Heath Rushing, and Thomas F. Curry Determining whether a data point is an "outlier" ? a result that doesn't fit, that is too high or too low, that is extreme or discordant ? is difficult when using small data sets (such as the data from three, four, or five conformance runs). The authors show that the Weisberg t-test is a powerful tool for detecting deviations in small data sets.