Statistics: T-test – #4496


Question: Suppose we’re interested in the effect of practice on public speaking anxiety. We recruit eight volunteers and pretest them on public speaking anxiety on a standardized test. We then provide the volunteers with several practice sessions in giving speeches and test them again. To see if the practice causes a lasting change in their anxiety, we administer a follow-up test 6 months later. Here are the data (higher scores indicate higher anxiety):

Pretest Posttest Follow-up
Volunteer 1 8 6 7
Volunteer 2 6 4 5
Volunteer 3 5 5 7
Volunteer 4 7 7 2
Volunteer 5 7 4 5
Volunteer 6 3 1 2
Volunteer 7 10 6 4
Volunteer 8 10 7 8

Compute F and test it for significance. If F is significant, use the LSD to do all pairwise comparisons.

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