Blog

We usually report the rate ratio when interpreting the effect of a covariate on survival time in an AFT model. How is the rate ratio expressed in terms of model coefficients? A)

The incidence rate is most appropriate when the hazard function is constant over time. To which distribution does this correspond?

Suppose a log-rank test is performed to compare survival outcomes in 4 groups. What are the degrees of freedom of the chi-square test that is performed?

Which of the following is the regression equation for failure time in an accelerated failure time model? Equation A:

Kaplan-Meier and Nelson-Aalen are

Consider a pair of regression models based on the same covariates with Model A: Surv(Time, Status) ~ Sex + Age + Genotype + Rx Model B: Surv(Time, Status) ~ Sex + Age + Genotype*Rx Considering ONLY the main effects coefficient for each of the covariates below, which estimates will have different interpretations in the two models? Ignore any potential numerical changes in the estimates themselves and focus on the actual meaning of the coefficients. Sex: [q1] Age: [q2] Genotype: [q3] Rx: [q4]

The Wald confidence intervals for parameter estimates are based on 

How many times will the value of the Kaplan-Meier estimator change?

How many unique cutpoints are used to compute the Kaplan-Meier and Nelson-Aalen estimators? (Don’t include time 0).

Suppose we ignored right-censoring in our sample by treating individuals as having died at the censoring time. Is there bias in our estimate of the survival curve? If so, in what direction?