Hi, I have using these stata commands to compute overall mortality rate in a seer dataset.

When using 1 variable,
- I obtain same IRR between stir race, strata(histo) and stmh race, by(histo). Is this normal?
- However, I have discovered that one can use several variables to adjust IRR rates when using stmh command but not for stir. For example, stmh race, by(sex histo) works but stir race, strata(histo sex) does not ?
- Last, stmc: what is the measure of time that stmc is using? my dataset contains 1 line per record and time unit is in month.

many thanks in advance
arnaud