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H524e-PS7-Solutions - H 524 Problem Set 7 Solutions Problem...

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H 524: Problem Set 7 Solutions Problem 1 A clinical trial designed to evaluate whether or not patients with coronary artery disease respond to treatments heparin and enoxaparin. Estimate RD = p H - p E RR = p H / p E OR = p H /(1- p H ) ÷ / p E / (1-p E ) where p H denotes the probability of not responding to heparin and p E denotes the probability of not responding to enoxaparin. Stata command: csi 309 266 1255 1341, or Stata output: | Exposed Unexposed | Total -----------------+------------------------+------------ Cases | 309 266 | 575 Noncases | 1255 1341 | 2596 -----------------+------------------------+------------ Total | 1564 1607 | 3171 | | Risk | .1975703 .1655258 | .1813308 | | | Point estimate | [95% Conf. Interval] |------------------------+------------------------ Risk difference | .0320445 | .0052195 .0588695 Risk ratio | 1.193592 | 1.028964 1.384559 Attr. frac. ex. | .1621929 | .0281492 .2777485 Attr. frac. pop | .0871611 | Odds ratio | 1.241258 | 1.035782 1.487492 (Cornfield) +------------------------------------------------- chi2(1) = 5.48 Pr>chi2 = 0.0192 a) Point estimates and 95% CIs Point estimate 95% CI RD 0.03 (0.01, 0.06) RR 1.19 (1.03, 1.38) OR 1.24 (1.04, 1.49)
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b) The confidence intervals for all 3 measures of association lead us to reject the null hypothesis that the two treatments have the same success probability. The p-value of 0.019 supports this conclusion. The probability of not responding is higher under heparin; the
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