Answer
Priori multiple-comparison designs plan ahead to make certain comparisons of the data collected.
Post hoc multiple-comparison designs allow the researcher to make certain compressions of the data after it is collected.
Work Step by Step
These designs allow for a limited number of pairwise comparisons to be made, and they limit the number of comparisons so that the additive effects of multiple comparisons will not become so large as to nearly guarantee a significant outcome by simply making a huge number of pairwise comparisons.
