Essay about Case Study

1646 Words Apr 4th, 2014 7 Pages
1. Table 8.1 shows results of an eight-center clinical trial to compare a drug to placebo for curing an infection. At each center, subjects were randomly assigned to two groups.

Table 8.1 Clinical Trial Data for Problem 1

a. Perform two different tests (Breslow-Day, and likelihood ratio test) for whether the drug effect on curing an infection is the same over eight centers.

i) Breslow-Day test:

The B-D test of homogeneity tests for whether the drug effect on curing an infection is the same over eight centers gave a chi2 = 8.0 with df=7 and p-value = 0.333. Therefore since the p-value is > 0.05, we fail to reject the null that the drug effect on curing an infection is the same over the eight centers. The drug effect
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What is your conclusion with regard to the effect of the drug on curing the infection? What is the odds ratio using the CMH method?

The OR for curing the infection comparing drug with placebo, adjusting for the centers is 2.175, with a p-value of 0.011 which is less than 0.05 and therefore significant. We can conclude that the drug is 2.175 times better at curing the infections after adjusting for centers compared to the placebo.

Using the CHM Method:

From the CMH method above, the combined OR=2.13, with a p-value of 0.0115 which is significant at the 0.05 level. Therefore the drug is 2.13 times more effective at curing the infection after adjusting for centers compared to the placebo

d. Perform a new logistic regression to find the odds ratio for curing the infection without adjusting for the centers. Which measure, adjusted, or unadjusted odds ratio, do you prefer to use when you investigate the drug effect on curing the infection?

From the output above, the OR without adjusting for centers is 1.5 with a p-value of 0.108 which is not significant at the 0.05 level. Therefore, I will prefer to use the adjusted measure when investigating the drug effect on curing the infection.

e. (Extra Credit) Perform a likelihood ratio test on whether the treatment is different among the centers, using the deviance measure. data medtreatment; input center drug treatment count; datalines; 1 1 1 11
1 1 0 25
1 0 1 10
1 0 0 27
2 1 1 16
2 1 0 4

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