Case Study Essay

1633 Words Apr 8th, 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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Using STATA clear . input center drug treatment count center drug treatment count

D= (-2lm) – (-2Ls)
= (-2x- 22.18071) –(-2*-22.18071)
=(44.36)-44.36 =0
Therefore, in testing the fit of model m, we fail to reject the null hypothesis that all the parameters that are in the saturated model but not in model M equals 0.

2. Table 8.2 shows results of a study about Y = whether a patient having surgery with general anesthesia experienced a sore throat on waking (1 = yes) as a function of D = duration of the surgery (in minutes) and T = type of device used to secure the airway (0 = laryngeal mask airway, 1 = tracheal tube).

Table 8.2 Data for Problem 2 on Sore Throat after Surgery

a. Fit a main effects model using these predictors. What is the predicted probability function? Interpret the signs of the parameter estimates.

Logit[P(Y=1)] =β0 + β1(D) +β2(T)
Logit[P(Y=1)] = -1.41734 + 0.06868 (D=1min) -1.65895(T=1) or
P(soreThroat/D,T)= Exp (-1.41734+0.06868D-1.65895T)[1+Exp(-1.41734+0.06868D-1.65895T)
The coefficient of duration of surgery is positive meaning the

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