Discussion:
Q: A researcher would like to determine if relaxation training will affect the number of headaches for chronic headache sufferers. For a week prior to training, each participant records the number of headaches suffered. Participants then receive relaxation training, and for the week following training the number of headaches is again measured. The change in number of headaches before and after training is as follows (minus signs indicate a reduction).
Difference scores: -5 -1 -4 -3 -6 -8 0 +1 -1
(a) Compute the mean and SS for the sample of difference scores.
(b) Do the results indicate a significant difference? Use a two-tailed test with α= .05.
A. Yes, the relaxation training has a significant effect.
B. No, the relaxation training hasn't any significant effect.
(c) Compute r2, the percentage of variance accounted for, to measure the size of the effect.