For each ROI within the mask, the program first computes the average
across the contrast values within each data set separately. It thus obtains two lists
of averaged contrast values, where the number of elements in each list corresponds
to the number of contrast images in the two gropus.
It then performs a two-sample t-test between these two lists
against the null hypothesis of "no difference" between the groups. Example:
vROItwosample_ttest -in1 cgroup1_*.v -in2 cgroup2_*.v mask mask.v -report liste.txt
This call prints the statistical analysis to the terminal and to an ASCII-file. A typical output may for instance look like this:
  ROI   |   addr   | mm^3   | t | z | p | ||
---|---|---|---|---|---|---|---|
1     | 0.11     | 0.41     | 44.50     | 70     | -2.176     | -1.941     | 0.0261 | 2     | 0.08     | 0.44     | 30.50     | 494     | -1.031     | -0.985     | 0.1623 | 3     | -0.05     | 0.26     | 30.50     | 494     | -0.629     | -0.609     | 0.2712 | 4     | 0.22     | 0.66     | 27.00     | 76     | -0.578     | -0.561     | 0.2874 | 5     | 0.67     | 1.04     | 13.00     | 61     | 0.553     | 0.537     | 0.2957 |
In this example, five ROIs were present. Only the first ROI shows a significant effect (p < 0.05). The ROI-size is given in mm^3. The address refers to the center of gravity of the ROI. It is given in Talairach coordinates.