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习题如下,一共7个问题.

To evaluate the rate of infection betweentwo different bathing method among 154 burn patients (burn.sd2), information onburn and wound infection was collected from medical record review as listedbelow:

Treatment: 0-routine bathing 1-body cleansing

Gender: 0-male 1-female

Race: 0-nonwhite 1-white

Percentage of total surface area burned

Burn site indicator : head 1-yes 0-no

Burn site indicator : buttock1-yes 0-no

Burn site indicator : trunk 1-yes 0-no

Burn site indicator : upper leg 1-yes 0-no

Burn site indicator : lower leg 1-yes 0-no

Burn site indicator : respiratory 1-yes 0-no

Type of burn:1-chemical 2-scald 3-electric 4-flame

Time to excision or on study time

Excision indicator: 1-yes 0-no

Time to prophylactic antibiotic treatmentor on study time

Prophylactic antibiotic treatment 1-yes 0-no

Time to straphylocous aureaus infection oron study time

Straphylocous aureaus infection 1-yes 0-no

问题1-7:

1. Choosing a tie option beforeconducting proportional Hazard Model and Justify why you make this choice.

2. Using Proportional Hazard Modelto explore the risk of infection for patients under different bathing methodsadjusted for confounders. Provide the estimated hazard ratio and its 95% CI forthe risk of infection between two different bathing methods.

3. Test the hypotheses of 9 (a)noassociation among four different types of burn on the time to infection, (b)the time to infection were similar between chemical/scald burn andelectric/frame burn, interpret your findings.

4. Test the proportionalityassumption using g(t)=log(t), Schoenfeld residuals, Marttingale residuals, andgraph approach for the variable for treatment (bathing methods) under theproportional hazard model from question2.

5. Estimate the adjusted survivalfunction for patients receiving different bathing methods.

6. Evaluate overall fit for thefinal model of question2. Determining the functional form of percentage oftotal surface to best explain its effect on the risk of infection. Checking foroutliers and influential observation in the final model.

7. Add two time-dependentcovariates –the effect of the timing of wound excision and the effect of thetiming on having prophylactic antibiotic into the proportional hazard model ofquestion2 and then summarize and interpret your findings from this model.