Question: Refer to Example, investigating the relationship between taking aspirin and risk of heart attack. As shown in Table of the 11,037 aspirin takers had heart attacks, whereas 189 of the 11,034 placebo takers had them. Carry out the chi-square test for this study. (The hypotheses are already given in this chapter.)
Example: Aspirin and Heart Attacks In Example, we learned about an experiment in which physicians were randomly assigned to take aspirin or a placebo. They were observed for 5 years and the response variable for each man was whether or not he had a heart attack. As shown in Table of the 11,037 aspirin takers had heart attacks, whereas 189 of the 11,034 placebo takers had them. Notice that the difference in percentage of heart attacks between aspirin and placebo takers is only 1.71% 0.94% 0.77%-less than 1%. Based on this small difference in percents, can we be convinced by the data in this sample that there is a real relationship in the population between taking aspirin and risk of heart attack? Or would 293 men have had heart attacks anyway, and slightly more of them just happened to be assigned to the placebo group? Assessing whether or not the relationship is statistically significant will allow us to answer that question.