This chapter of the NIST Engineering Statistics handbook "presents the background and specific analysis techniques needed to compare the performance of one or more processes against known standards or one another." It contains an introduction and information about comparisons with one process, two processes, and three or more processes or samples. Topics include outliers, trends, confidence intervals for means and proportions for one sample. Also included are materials on ANOVA, Kruskal Wallis tests, tests for equivalence of variances, variance components, chi-square tests for contingency tables and multiple comparisons.