19. There is an interpretation diffi culty with Pro blem 18. It is clear that the headaches decreased signifi cantly. However, it is possible that the decrease was not due to the biofeedback training but rather to some other aspect of the situation, such as the attention shown to the subjects. What is really needed is a group to control for this possibility.

Assume another group of nine headache patients was run at the same time as the group in Problem 18. This group was treated in the same way except the subjects did not receive any training involving biofeedback. They just talked with you about their headaches each week for 6 weeks, and you showed them lots of warmth, loving care, and attention. The numbers of headaches for the baseline and 2-week follow-up period for the control group were as follows:

Evaluate the effect of these other factors, such as attention, on the incidence of headaches. Use 0.052 tail. clinical, health

No. of Headaches Subject No. Baseline I Follow-up 5 4 23 89 34 1 12 46 1.15 5 64 6 53 7 80 9 8 7 6 97