Reply-To: | | [log in to unmask][log in to unmask] > >> CC: [log in to unmask] > > > >> > >> The null hypothesis is defined before you create the contrasts. The > >> contrasts are based on your null hypothesis. > >> > >> You should not be testing group differences in a 1st level model; > >> rather, you should take estimates of the first level model from each > >> subject to the second level random effects model. > >> > >> Best Regards, Donald McLaren > >> ================= > >> D.G. McLaren, Ph.D. > >> Research Fellow, Department of Neurology, Massachusetts General Hospital > >> and > >> Harvard Medical School > >> Postdoctoral Research Fellow, GRECC, Bedford VA > >> Website: http://www.martinos.org/~mclaren > >> Office: (773) 406-2464 > >> ===================== > >> This e-mail contains CONFIDENTIAL INFORMATION which may contain PROTECTED > >> HEALTHCARE INFORMATION and may also be LEGALLY PRIVILEGED and which is > >> intended only for the use of the individual or entity named above. If the > >> reader of the e-mail is not the intended recipient or the employee or > >> agent > >> responsible for delivering it to the intended recipient, you are hereby > >> notified that you are in possession of confidential and privileged > >> information. Any unauthorized use, disclosure, copying or the taking of > >> any > >> action in reliance on the contents of this information is strictly > >> prohibited and may be unlawful. If you have received this e-mail > >> unintentionally, please immediately notify the sender via telephone at > >> (773) > >> 406-2464 or email. > >> > >> > >> On Wed, Dec 5, 2012 at 9:02 AM, Qasim Bukhari <[log in to unmask]> > >> wrote: > >> > Dear SPM Expert, > >> > I m trying to run an analysis differentiating between the two > >> > population. I > >> > have two groups, group 1 and group 2. These two group differ under one > >> > of > >> > the regressor; which is an extracted time series of region R1. I tried > >> > to > >> > run 3 different experiments > >> > > >> > Experiment 1: group 1 vs group 1 : fixed effect analysis > >> > I input two different subjects but both from group 1. Under the multiple > >> > regressors; I input the extracted time series of region R1. In order to > >> > see > >> > the results; I defined an F-contrast, with (1,1) imagining that its the > >> > same > >> > group so the contrast should also be the same. However in the result; I > >> > see > >> > quite a lot activations. I wasnt expecting that, since these are from > >> > the > >> > same population > >> > > >> > Experiment 2: group 2 vs group 2 : fixed effect analysis > >> > I did the same procedure as described above however this time for group > >> > 2. > >> > The results were same as mentioned above; while I was expecting > >> > contrary. > >> > > >> > Experiment 3: group 1 vs group 2 : fixed effect analysis > >> > This time, I input different subjects from the different groups; however > >> > I > >> > kept the F-contrast as 1, 1. Again I see a lot of activations in the > >> > result, > >> > and I dont have any explanation for this actually > >> > > &gÿ†>t |