After having performed an F-test (one-way ANOVA, two-way ANOVA,…) which has indicated that there exists a difference between the group means, post hoc tests help defining which group means are significantly different from each other. Such tests are never to be used when the F-test does not show the existence of significant differences. Note that some parameters in post hoc tests must be carefully chosen based on the experimental design to avoid “false positive”.
