When comparisons are planned in advance of conducting the experiment, you need a significant value for F obt before you can make the comparisons.

Question

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Planned (a priori) comparisons can be made based on the overall F-test from an ANOVA, but they do not necessarily require a significant F-value to proceed. These comparisons are decided before looking at the data and are often based on theoretical predictions or research questions.

When Comparisons Are Planned in Advance of Conducting the Experiment