USE RCMDR. [8 marks] Question 2 Researchers looked at the association between ph
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USE RCMDR.
[8 marks] Question 2 Researchers looked at the association between physical activity and heart disease. Of the 10,239 women in the study who had low levels of physical activity (less than 200kcal/wk), there were 101 cases of heart disease. Of the 9877 women with physical activity measured between 200 and 600kcal/wk, there were 56 cases of heart disease. Source: Physical Activity and Coronary Hearty Disease in Women by Lee, Roxrode et al., Journal of the American Medical Association, 285(11) (a) Find a 95% confidence interval for the difference in the proportions of women with [4 marks] (b) Does it appear that physical activity is associated with heart disease in women? Give 4 marks] heart disease for the two groups. an informative response, with reference to the result in (a).Explanation / Answer
Solution
(a) 95% confidence interval : (p1-p2)+- 1.96 p1(1-p1)/n1 + p2(1-p2)/n2))0.5
where p1 = 101/10239 = 0.01 p2 = 56/9877 = 0.006
95% CI = ((0.01-0.006) +- 1.96 ((0.01)(0.99)/10239 + (0.006)(0.994)/9877)0.5
CI = (0.0015, 0.0065)
(b) Yes, physical activity reduces the proportion of heart disease
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