A staff member at UF's Wellness Center is interested in seeing if new stress reduction program will lower employees high blood pressure levels. Twenty people are selected and have their blood pressure measured. Each person then participates in the stress reduction program. One month after the stress reduction program, the blood pressure levels of the employees were measured again. Did the program reduce the average blood pressure level? (mud = population mean difference = before - after)
A. Ha: mud = 0
B. Ha: mud > 0
C. Ha: mud < 0
D. Ha: mud does not equal 0