We apply the t-test when we compare two groups; two or more groups can be compared using an ANOVA. The current version of the application has a one-way ANOVA for comparing several means. Note that the F-test produced by ANOVA test the hypothesis that all population means are equal. The alternative hypothesis is that at least one of the population means differs from the others. The statistical model in ANOVA is
where yij is the observation of individual j in group i, u_i is the population mean in group i, and e_ij is an error term.