Dear FSL experts,
Does unbalanced group size affect the variance calculation and therefore whether the groups should be entered separately in the design matrix?
I am running a simple "Unpaired Two-Group Difference (Two-Sample Unpaired T-Test)" using "randomize" on DTI-FA data, in which I am not expecting the brains of each group to be wildly different as you might for certain patient groups. I have therefore elected to model them in a single group for the purposes of variance. However, I have unequal group sizes: N= 16 and 23. My questions are:
1) Should this imbalance be taken into consideration when deciding how to model the groups?
2) Would be better to leave some subjects out to have N=16 in both groups?
3) Is there some way of calculating or quantitatively supporting my equal variances assumption?
Best regards,
Emily