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Hi fundamentally this isn't such a problem - if I understand your study correctly you'll be dealing with a paired t-test comparison, i.e. what is relevant is the t2-t1 difference and not the comparison A vs B at t1. For peace of mind you should verify that t2-t1 for the control population is centered at 0 - that's the relevant null assumption to test against. hth Christian On 3 Jul 2008, at 10:49, Anna Rieckmann wrote: > Hi all > > I am looking for fMRI expert opinions on the following situation: > > We have data from an intervention study over two time points. The > aim of the > study was to compare changes in activations during a cognitive task > over > time between the treatment and the control group. > Unfortunately, the two groups are not equal at baseline. Although > allocation > to groups was random, the intervention group happens to show much > stronger/more activations at baseline. This makes it obviously hard to > attribute the changes in activation over time to the treatment > rather than > the baseline activation. > > I am wondering if there is a good way to statistically control for > baseline > activation when looking at the change over time or whether we should > accept > the situation as it is and not proceed any further with this data. > Any opinions are much appreciated! > > Thanks > > Anna