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- Say you have a contrast C = [1 -1 0]', and for a certain voxel, you have beta = [1 4 2]'. The COPE is simply C'*beta = [1 -1 0] * [1 4 2] = 1*1 -1*4 + 0*2 = -3. This is what goes in the numerator of the t statistic.
- - The *pe* are the parameter estimates, also known as betas (this image has as many volumes as regressors in the design);
- The *cope* are the contrasts of parameter estimates, one image per contrast. It's the inner product between the contrast vector and the betas;- Because the *pe* are estimates, so are the *cope*. These estimates have an uncertainty surrounding them, and the variance around these estimates is the *varcope*;- The *sigmasqr* is the variance of the residuals. The sigmasquareds volume is the unbiased estimate of the noise standard deviation in the GLM.
To view group differences in mricron:
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