I guess my question comes in two parts:
Following a 1x7 repeated-measures ANOVA, I carried out 3 pre-planned tests. Two were t-tests between 2 of the conditions. The third is a 1x6 ANOVA (to test significance between conditions 2-7). My question is:
Do I have to apply the Bonferroni correction to all 3 tests, or just the 2 tests? I.e. should the significance level be 0.05/3 = 0.017 for all 3 tests?
As above, I carried out a 1x7 repeated-measures ANOVA, and 3 pre-planned tests (2 t-tests and a 1x6 ANOVA). In the original 1x7, sphericity was assumed, so I report the 'sphericity-assumed' statistic, and it is non-significant. Next, despite this non-significance, I decided I should do the pre-planned tests for the sake of completeness. When I do the 1x6 repeated measures ANOVA, sphericity is NOT assumed, so I use the Greenhouse-Geisser values, and it comes up significant (if I were to use the shericity assumed values, it would be non-significant). My problem here is that the ANOVA using just 6 of the 1x7 conditions is coming up significant when the original 1x7 was non-significant. Logically, this doesn't seem to make sense to me.
Is there some 'rule of thumb' whereby the use of Greenhouse-Geisser values needs to be consistent?
I hope this makes sense. I have trawled the internet. I have looked at more stats books than you can shake a stick at. But nothing comes close to discussing this sort of situation.