Thus, we see that the 95% confidence interval for the hazard ratio in Example 1 of Log-Rank Test is (.646, 3.730), as shown in Figure 1 (with references to the cells in Figure 3 of Log-Rank Test). This approximation is fairly good for values of h between 1/3 and 3. Relative risk (RR), or risk ratio, is an estimate the magnitude of an association between an exposure and a disease, giving the likelihood of developing the. Since h > 1, the drug in trial B has a more favorable survival rate than the drug in trial A (in fact 55% more favorable).Ī confidence interval for h can be calculated based on the fact that ln h is approximately normally distributed with standard error Thus the hazard ratio h (of A to B) is 1.55.
For two survival distributions, the ratio of the failure rates is called the hazard ratio (aka the relative risk or risk ratio), i.e.įor Example 1 of Log-Rank Test, the failure rates of trials A and B are 12/9.828 = 1.221 and 8/10.172 =. Definition 1: The ratio of the observed number of failures (“deaths”) divided by the expected number of failures d/ e (using the terminology from Log-Rank Test) is called the failure rate.
