Since the control group in Problem 19 also showed significant reductions in headaches, the interpretation of the results in Problem 18 is in doubt. Did relaxation training contribute to the headache...

Since the control group in Problem 19 also showed significant reductions in headaches, the interpretation of the results in Problem 18 is in doubt. Did relaxation training contribute to the headache decrease, or was the decrease due solely to other factors, such as attention? To answer this question, we can compare the change scores between the two groups. These scores are shown here:

What is your conclusion? Use??
= 0.052 tail.