Editing Analysis of variance (section)

====Follow-up tests====
A statistically significant effect in ANOVA is often followed by additional tests. This can be done in order to assess which groups are different from which other groups or to test various other focused hypotheses. Follow-up tests are often distinguished in terms of whether they are "planned" ([[A priori and a posteriori|a priori]]) or [[Post-hoc analysis|"post hoc]]." Planned tests are determined before looking at the data, and post hoc tests are conceived only after looking at the data (though the term "post hoc" is inconsistently used).

The follow-up tests may be "simple" pairwise comparisons of individual group means or may be "compound" comparisons (e.g., comparing the mean pooling across groups A, B and C to the mean of group D). Comparisons can also look at tests of trend, such as linear and quadratic relationships, when the independent variable involves ordered levels. Often the follow-up tests incorporate a method of adjusting for the [[multiple comparisons problem]].

Follow-up tests to identify which specific groups, variables, or factors have statistically different means include the [[Tukey's range test]], and [[Duncan's new multiple range test]].  In turn, these tests are often followed with a [[Compact Letter Display (CLD)]] methodology in order to render the output of the mentioned tests more transparent to a non-statistician audience.