Example of a paired t-test (repeated measures) with 4 observations/subjects. The first four columns of the design matrix each model a within-subject mean. The final column models the between-group difference.   
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DESIGN MATRIX:
   1  0  0  0  1
   0  1  0  0  1
   0  0  1  0  1 
   0  0  0  1  1
   1  0  0  0 -1
   0  1  0  0 -1
   0  0  1  0 -1
   0  0  0  1 -1

CONTRAST (Group 1 > Group 2):
 0 0 0 0 1

STATISTICAL TEST:
t-test

EXCHANGE BLOCKS:
1 2 3 4 1 2 3 4 
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