Reply-To: | | [log in to unmask][log in to unmask] >> > wrote: >> >>> On Tue, Oct 1, 2013 at 4:14 PM, fMRI <[log in to unmask]> wrote: >>> >>>> Hi all, >>>> >>>> I am confused about which test or model I should select. >>>> >>>> I have scanned 8 subjects. Each subject was scanned in two sessions, >>>> left and right hand. Each session consists of three conditions: A, B & C. >>>> So basically I have from each subject six conditions using both hands. >>>> >>>> In the first level, i defined each condition in a separate regressor. >>>> Then I contrast each condition versus rest. So I have in each session : >>>> A>rest, B>rest, C>rest. >>>> >>>> So I end up by three contrast images per session or six per the two >>>> sessions. >>>> >>>> I am interested in comparing right versus left. So I would like to >>>> compare first A from session 1 versus A from session 2 and so on. >>>> >>>> I thought first to use two sample t-tests by taking the con from each >>>> subject in session 1 and condition A and compare that to session 2. And >>>> then do the same for Conditions B & C. >>>> >>>> Is this the right way to do it? >>>> >>> >>> No. You only have one sample. To compare two conditions from the same >>> subjects you need to use a paired t-test or create difference images for >>> the two sessions and use a one-sample T-test. The results will be the same. >>> >>> >>>> >>>> Or are there better options such as ANOVA? Can anyone please explain >>>> what should I select an how I should do this ? >>>> >>> >>> Flexible factorial (see my previous posts) can be used to compare 2 or >>> more conditions. This is basically a repeated measures ANOVA. >>> >>> >>>> >>>> Another consideration that it might be of interest is that I may need >>>> then to compare A1 versus B2 or C2 or B2+C2. >>>> >>> >>> I'm not quite sure why you would want to compare condition A from the >>> left hand to Conditions B and C with the right hand. Nevertheless, for A1 >>> vs B2 or C2, its paired t-test as above. If you want A1 vs B2+C2, I'd would >>> advise you to compare A1 to B2+C2 instead as two conditions will usually be >>> higher than 1. For A1 vs (B2+C2)/2 [which doesn't make sense due to >>> different hands], you'd create a contrast image for (B2+C2)/2 then use a >>> paired t-test. You could also use a flexible factorial with the contrast of >>> 1 -1/2 3$ |