# Post-hoc corrections for multiple t-tests

I am comparing two groups (young vs. old adults) for differences in 5 brain regions (size) with independent t-tests. I also compare performance on three different aspects of a task with independent t-tests and then correlate brain sizes and behavioral performance . I adjusted my p-values (Bonferroni-method) for the correlations (for the five brain regions), but I am not sure, how exactly/if I have to adjust the p-values for each independent t-test between the age groups. I have a priori hypotheses about all comparisons. Any help would be highly appreciated!

• Welcome to Cross Validated, Isabel. Before asking how to correct for multiple comparisons, you might consider whether you should correct. See here for some discussion: stats.stackexchange.com/questions/3200/… – Michael Lew Nov 21 '18 at 20:08

If your study is preliminary, or if it is about characterisation rather than testing hypotheses then you probably should not correct' for multiple comparisons. The raw P-values give you the strength of evidence against the individual null hypotheses and are should be presented alongside a more detailed presentation of the data.