November 30, 2011 5:51 PM Subscribe
What does "posthoc" mean?
posted by cnanderson to science & nature (7 answers total) 1 user marked this as a favorite
Settle a semantics argument I am having with a colleague. Suppose I run an ANOVA analysis on 3 populations: A,B,C. I consider the only informative posthoc comparisons of the initial F test to be the pairwise ones: A vs B, A vs C and B vs C.
My colleague contends that another informative “posthoc” comparison would be to redefine the populations by comparing a single population to a “new” population formed by pooling together the measurements of the other two levels : A vs BC, B vs AC, C vs AB.
My contention is that once you go back and redefine what a population is, then that is a brand new question and no longer a “posthoc” analysis of the initial F test. The results may be interesting, but ought not to be used to interpret the F test. My colleague insists otherwise and claims that both pairwise comparison and comparisons made by pooling populations ought to be termed "posthoc" . Who is correct?