The following study is a very famous medical study called the Physicians\' Healt
ID: 3021923 • Letter: T
Question
The following study is a very famous medical study called the Physicians' Health Study I. It was begun in 1982 and involved 22,071 male physicians between the ages of 40 and 81. One of the goals of the study was to determine if taking 325 mg of aspirin every other day would reduce a man's risk of a first heart attack. This was a randomized clinical trial which means each subject in the study was randomly assigned one of two treatments - taking an aspirin every other day or taking a placebo every other day. About 11,000 subjects were randomly assigned to take an aspirin every other day, and about 11,000 subjects were randomly assigned to take a placebo every other day. The study lasted 5 years. At the end of the study, the researchers described their results by reporting the percentage of heart attacks in the group taking aspirin and in the group taking a placebo. They found 0.9% of the group taking aspirin and 1.7% of the group taking a placebo had heart attacks. They used statistical methods to predict that US men aged 40 or older who take aspirin every other day have a lower risk of having a first heart attack compared to men who don't take an aspirin every other day. Match each term with the aspect of the study to which it refers: Design a. The use of statistical methods to make the prediction that US men aged 40 or older who take aspirin every other day have a lower risk of having a first heart attack compared to men who don't take an aspirin every other day. Inference b. The sample, the randomization (random assignment of treatment), and the plan to obtain percentages of each group that have heart attacks. Description c. The actual percentages of the people in the sample who have heart attacks.
Explanation / Answer
Ho:there is no significant difference of US men aged 40 or older who take aspirin every other day have a lower risk of having a first heart attack compared to men who don't take an aspirin every other day .
H1:there is a significant difference of US men aged 40 or older who take aspirin every other day have a lower risk of having a first heart attack compared to men who don't take an aspirin every other day .
Given 0.9% of the group taking aspirin and 1.7% of the group taking a placebo had heart attacks, then
p1=99/286=0.3461, p2=10901/21714=0.502, P=[(n1p1)+(n2p2)]/(n1+n2)=0.5, Q=1-P=0.5, Z=[(p1-p2)]/[(PQ[(1/n1)+(1/n2)])]=(.502-0.3461)/[0.5*0.5*(.0035)]=0.1559/0.0296=5.2669>1.96[the table value of Z at 5% level of significance],so we reject Ho, then we accept H1. Therefore, there is a significant difference of US men aged 40 or older who take aspirin every other day have a lower risk of having a first heart attack compared to men who don't take an aspirin every other day .
Percentages who have heart attacks
Take everyother day dont take everyother day total Aspirin 99 10901 11000 Placebo 187 10813 11000 Total 286 21714 22000Related Questions
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