3) We did consider as another comparison population, the continuous FFS population using the 5-percent Medicare sample.
13) NOTES: In parentheses are the t-statistics for comparison of means between the treatment population and the two comparison populations.
SMRs provide a popular approach to comparing mortality in a specific population with mortality from a suitable comparison population (17).
There are three options for the baseline hazard: model the hazard without including a comparison population, treat the comparison population as an unexposed group, or replace the baseline hazard function with empirical estimates based on the comparison population (not included in Table 1).
Using the log-transformation without the comparison population gave a good model fit, according to AIC, but risk estimates were not easy to interpret because of instability of the fitted model at low dose.