Hi
I am trying to set up a simple SPM unpaired T test comparing a single patients TcHMPAO SPECT data set with a 20 controls (studies that have been reported as "normal"). I am using SPM8b with the following basic model parameters: Two Sample T-test, Threshold Masking: Relative, Global Calculation: Mean, Global Normalistation: Yes, Normalisation: Proportional.
I have found an article on the web by Rik Henson (MRC) on this subject and the Two-Sample T-test appears to be recommended. This articles suggests I should be able to use the T-contrast [1 -1] to test the control group against the single patient, however SPM tells me this is and invalid contrast. The only contrast it allows is [0 1]. I would be very grateful if someone could explain what I am doing wrong. Presumably I should be able to set up a contrast that will test for areas where the single patient is greater that the control group and also a contrast that test for areas where the single patient is less than the control group.
Many Thanks
Dudley
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