Time ratio - survival analysis

[Am Ab]

I am looking at the determinants of the timing of the first prenatal visit. Using the Accelerated Failure Time model I have a time ratio of 0.47. Is it possible to convert this into weeks? If so how is it done?

[Clyde Schechter]

No, it's not possible to convert this into weeks, or any other unit. That accelerated failure time ratio is dimensionless: it is the ratio of the time to prenatal visit when the variable it is attached to is 1 vs the time to prenatal visit when the variable it is attached to is 0. (I'm assuming the variable in question is a dichotomous variable here.) The ratio will be the same regardless of whether the original times were measured in weeks, days, eons, or picoseconds.

[Andrea Discacciati]

@OP: you might want to look into quantile regression for censored outcomes (for example, laplace regression, see http://www.stata-journal.com/article...article=st0294 and references therein).