Post Hoc tests

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”.

Post hoc tests are commonly used as a follow up of F-test (such as ANOVA, factorial ANOVA, …). These tests may only be performed if the F-test shows that there exists a significant difference between the means of the tested groups. If not, post hoc tests are not be used! […]

Post-Hoc Tests

Skjermbilde 2016-08-08 14.56.25
Tukey’s Honest Significant Difference (HSD) test is a post hoc test commonly used to assess the significance of differences between pairs of groups. This applies for example to one-way ANOVA, factorial design ANOVA, … As usual, the null hypothesis states that the means of the tested groups are equal. The […]

Post Hoc Tests – Tukey HSD

Skjermbilde 2016-08-08 13.01.54
The function pairwise.t.test() allows for performing multiple t-tests on a multitude of groups using all possible pairwise comparisons. This comes handy as a follow up to one-way ANOVA, two-way ANOVA, … In addition, these pairwise t-tests assume normality of distribution and equality of variances which you needed anyway to perform ANOVA. This […]

Post Hoc Tests – Pairwise Comparisons with corrections