Contents
What does a significant interaction in ANOVA mean?
When an interaction effect is present, the impact of one factor depends on the level of the other factor. Part of the power of ANOVA is the ability to estimate and test interaction effects. When interaction effects are present, it means that interpretation of the main effects is incomplete or misleading.
What does it mean when an interaction is significant?
A significant interaction effect means that there are significant differences between your groups and over time. In other words, the change in scores over time is different depending on group membership.
How many main effects does a 3 way ANOVA have?
7 main effects
“Descriptive” effects in a 3-way The 3-way — significant or not — is always descriptive ! With 7 main effects and interactions (and myriad simple effects) you have to be careful to get the correct part of the design that is “the replication” of an earlier study.
How can I explain a three-way interaction in ANOVA?
In our model we have three independent variables, a, b, and c, and we believe that there is a three-way interaction. First we need to test whether there is a significant three-way interaction. The A*B*C* interaction is statistically significant. Next, we need to select a two-way interaction to look at more closely.
Which is an example of a three way interaction?
We will use a small artificial dataset called threeway that has a statistically significant three-way interaction to illustrate the process. In our example dataset, variables a, b, and c are categorical.
When to use Bonferroni correction in three way ANOVA?
If you want to emphasize the differences that you will notice then you may apply standard statistical methods (t – test, Kruskal Wallis etc) and confirm the differences with a statistical test. Keep in mind that in that case it is a good idea to make a Bonferroni correction for the rejection level.
How to use the contrast statement to understand a three?
There are at least four different methods of determining the critical value of tests of simple main-effects.