## What is the post-hoc test for 2 way ANOVA?

Post-hoc testing ANOVA will tell you which parameters are significant, but not which levels are actually different from one another. To test this we can use a post-hoc test. The Tukey’s Honestly-Significant-Difference (TukeyHSD) test lets us see which groups are different from one another.

**What does Tukey’s post hoc tell you?**

Tukey’s Honest Significant Difference (HSD) test is a post hoc test commonly used to assess the significance of differences between pairs of group means. Tukey HSD is often a follow up to one-way ANOVA, when the F-test has revealed the existence of a significant difference between some of the tested groups.

**When should a Tukey post-hoc test be used?**

The Tukey post-hoc test should be used when you would like to make pairwise comparisons between group means when the sample sizes for each group are equal. If the sample sizes are not equal, you can use a modified version of the test known as the Tukey-Kramer test.

### How does Tukey test work?

The value of the Tukey test is given by taking the absolute value of the difference between pairs of means and dividing it by the standard error of the mean (SE) as determined by a one-way ANOVA test. The SE is in turn the square root of (variance divided by sample size).

**Do you need to perform a post hoc on an ANOVA that only has two levels for each main effect?**

Hi Javier! You can run post hoc if it has a main effect, but only for differences within the factor you found a main effect.

**What is a Tukey test used for?**

Tukey’s range test, also known as Tukey’s test, Tukey method, Tukey’s honest significance test, or Tukey’s HSD (honestly significant difference) test, is a single-step multiple comparison procedure and statistical test. It can be used to find means that are significantly different from each other.

#### Should I use Tukey or Scheffe?

If you only want to make pairwise comparisons, run the Tukey procedure because it will have a narrower confidence interval. If you want to compare all possible simple and complex pairs of means, run the Scheffe test as it will have a narrower confidence interval.