Question

In a study to test the effects of low-dose aspirin in the prevention of heart disease, 22,071 U.S. male physicians ages 40-84 in the year 1982 were randomly assigned to be in either the low- dose aspirin group or the placebo group. Each participant was required to take the assigned pill every other day for five years. The study was double blind. Of the 11,034 physicians the placebo, 189 suffered heart attacks during the study. Of the 11, 037 physicians who took aspirin, 104 had heart attacks. Answer all four parts: a) State the null hypothesis using "association" wording. (2 points) b) Fully define the parameter Copy Look Up Share... for this study. (1.5 points) c) Give the notation for the other parameter in this study. (0.5 points) d) State the null and the alternative hypotheses using the symbols you defined in questions (b) and (c). Do not use subtraction. (1 point)

Answer 1

1)null hypothesis : there is no association between low dose - aspirin(Intervention) and heart disease(response)

2) the given study is a cohort study , and the parameter used to define the population is Relative risk(RR) or Risk ratio

$Relative-risk(RR) =\frac{the.probability.of.event.occuring.in.the.intervention.group}{the.probability.of.event.occuring.in.the.placebo.group}$

Consider the table

	intervention	placebo
event	a	b
no event	c	d

$Relative-risk(RR) =\frac{a/(a+c)}{b/(b+d)}$

here the intervention is aspirin , and the event is heart disease (heart attack)

if RR < 1 , low risk , if RR = 1 , no difference if RR > 1 , high risk

3) Risk is number of new cases of disease over a period of time ie., risk = (number of new cases / existing cases from the start of the study)

4) null hypothesis : There is no association between intervention and placebo ie.,RR < 1   alternative hypothesis: There is association between intervention and placebo ie., RR $\geq$ 1 ,