Hello, I am trying to determine a statistical difference, but am having
some difficulty determining what test should be used.
I have two timecourse measures, A and B. At 20 consecutive intervals, A
and B are measured, and the results are plotted. Both signals rise quickly
to about the same height, then fall. Sometimes A stays elevated longer.
There are eight seperate trials (representing eight conditions), producing
eight pairs of curves.
I want to show that in some conditions, the difference between the length
of A's response and B's response is greater than in other conditions:
duration(A) - duration(B) is significantly greater in some conditions.
I tried a t-test for each condition, subtracting B from A at each interval
and using a t-test to determine if the resulting sample differed from 0.
Unfortunately, in a couple conditions where it appears the A response is
about the same as the B response, but the t-test is so sensitive that even
small differences between A and B produce significance. The t value for
the condition (#1) which it is important to demonstrate has a longer A
duration (as is clearly obvious on inspection) is over 38. The conditions
in which A - B is minimal still have significant t's of 5 or 8 (when a p
of .05 requires a t of around 2).
So according to the test I've chosen, A-B in almost all of the conditions
is significant. What test will allow me to reveal the much greater
significance of condition #1 relative to the others? I thought of
chi-square (sum(A), sum(B) for all intervals; crossed with 1-8), but as
chi-square is for frequency data, I'm not sure if it's applicable here.
Thanks for any guidance,
Jim
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