Two sample tests are used to test whether two samples of data could have come from the same population. For example, we might be interested in comparing results from an experiment with those from a control experiment. Two sample tests compare the values of the sample statistic observed in the two different samples. When more than two samples need to be tested (e.g. 3 experiments), instead of performing two sample tests between all pairs of possible samples, it is better to use a more integrated multiple testing approach such as ANalysis Of VAriance (ANOVA). See Von Storch and Zwiers (1999) for more discussion.