I am desperately hoping for your quick help... Would you please cross-validate ;) my statistical proceedure and help me solve a huge problem (see c)??
So imagine there is an experiment to test a treatment and a control group. It consists of
a) behavioural tests (Test 1, Test 2)
b) questionnaires (metric scores were derived, so Q1, Q2, Q3...)
c) EEG-experiment with a test with two conditions within it (A and B)
The question is, whether the groups differ, and if, where exactly.
So to test this
for a) I can use for each test (1 and 2) either independent t tests (for normally distributed values) or Mann-Whitney U test (for not normally distributed values), with p-values corrected (Sidak)
OR should I use two-way ANOVAs for each test (values as within, group as between factor)?
for b) same as a) ?
for c) If I was to concider 2 electrodes (since I do not know where exactly to expect the effects) and have 2 conditions (A and B) in two groups (treated vs control) do I choose the three-way mixed design ANOVA (2x2x2)?
OR may I concider each electrode seperately to run a two-way mixed design ANOVA with condition as within and group as between factors. Or would that yield an alpha-error accumulation?
May I do post hoc tests if there is no three-way interaction, but only two-way? And when I do any of these, SPSS refuses to do post-hoc tests ("there are not more than two groups"), so do I use independent t tests for any significant interactions?
I am aware that it is a lot, but hope you might be so kind to help me!!
Thank you in advance