Cardiovascular disease is a major cause of death and illness worldwide, with high blood pressure and high LDL cholesterol both being established risk factors. Because most cardiovascular events occur in persons with average risk factors. Because most cardiovascular events occur in persons with average risk and no previous cardiovascular disease history, the present research examined the simultaneous use of both blood pressure reducing drugs and cholesterol reducing drugs on this population, rather than focusing on only those on only those at high risk. Subjects included men at least 5 years old and women at least 6565 years old without cardiovascular disease who had at least one additional risk factor besides age, such as recent or current smoking, hypertension, or family history of premature coronary heart disease. Those with current cardiovascular disease were excluded from the study. Subjects were randomly assigned to the treatment (cholesterol and blood pressure reducing drugs) or a placebo, and the number suffering the primary outcome of a fatal cardiovascular event, a nonfatal myocardial infarction or a nonfatal stroke, were observed. Provided are the results for the two groups over the course of the study:

Group Sample size Number experiencing primary outcome
Treatment 3180 113
Placebo 3168 157

Let p1 be the proportion experiencing the primary outcome with the treatment and p2 the proportion without the treatment. Select the correct pair of hypotheses.

a. H0:p1=p2 versus Ha:p1â p2 .
b. H0:p1=p2 versus Ha:p1>p2 .
c. H0:p1=p2 versus Ha:p1 d. None of the options are correct.