02-17-2012 06:54 AM
i performed a T-test, and for the C.I. , I got 3 lines in the t-test about this.
The first is for "group A" second is for "group B" and third is for "Diff(Group A - Group B)"
Now, I NEED TO DO AN ANALYSIS ON THE VARIABILITY OF GROUP A AND GROUP B, whether I should use the line "Diff(Group A- Group B)" or the calculations that I get by myself from the subtraction of lower bound of CI and upper bound of CI in different groups?
02-17-2012 08:21 AM
The first line tests whether the mean of group A is different from zero, the second whether the mean of group B is different from zero, and the third whether the difference between A and B is itself different from zero. Beware of subtracting between confidence bounds--you could have a significant difference without the difference being greater than zero. And it scares me a little that you have multiple groups and are using multiple t-tests to compare them two at a time. That sort of comparison is handled a lot better by analysis of variance techniques.