Q1) Researcher would like to find out if relaxation training will affect number of headaches for chronic headache sufferers. For week prior to training, each participant records number of headaches suffered. Participants then get relaxation training, and for week following training number of headaches are again measured. 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) Calculate mean and SS for sample of difference scores.

b) Do results indicate a significant difference? Use two-tailed test with α = .05.

i) Yes, relaxation training has a significant effect.
ii) No, the relaxation training hasn't any significant effect.

c) Calculate r², percentage of variance accounted for, to measure size of the effect.