Implement the test in Problem 8.94, and report a p-value?

Hypertension

A study was performed comparing different nonpharmacologic treatments for people with high-normal diastolic blood pressure (DBP) (80−89 mm Hg). One of the modes of treatment studied was stress management. People were randomly assigned to a stress management intervention (SMI) group or a control group. Participants randomized to SMI were given instructions in a group setting concerning different techniques for stress management and met periodically over a 1-month period. Participants randomized to the control group were advised to pursue their normal lifestyles and were told that their blood pressure would be closely monitored and that their physician would be notified of any consistent elevation. The results for the SMI group (n = 242) at the end of the study (18 months) were as follows:

Mean (change) = −5.53 mm Hg (follow-up – baseline), sd (change) = 6.48 mm Hg.

8.94 What test can be used to assess whether mean blood pressure has changed significantly in the SMI group?