Examine the data in Table 21.5, which report the outcomes for the Physician€™s Health Study that assessed the effect of a low-dose aspirin regimen on risk of heart attack.
a. For the group of patients that had the low-dose aspirin regimen, calculate the odds of death.
b. For the group of patients that received placebo, calculate the odds of death.
c. Compute the odds ratio that tells us how much more likely a heart attack was for patients in the placebo group (compared with the aspirin group).
d. Compute the odds ratio that tells us how much less likely a heart attack was for patients in the aspirin group (compared with the placebo group).
e. In simple language, how did the aspirin regimen change the odds of heart attack?
f. Now look at the data in a different way. What percentage of the aspirin regimen group had a heart attack? What percentage of the placebo group had a heart attack? Does looking at these two percentages give you a different impression about the impact of aspirin?
g. Describe two different statistical analyses that you could apply to these data to assess whether heart attack is significantly related to drug regimen. (Hint: for a 2 ï‚´ 2 table, simpler analyses were described in earlier chapters.)
Table 21.5 Data from an Experiment to Assess Effect of Low Dose Aspirin on Risk of Heart Attack in Men.

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Placebo (X 0) 10,845 Low Dose Aspirin (X = 1) 10,933 No Heart Attack (Y 0) Heart Attack (Y= 1) 189 104