Hi,

I got a quick question on setting survival data using -st set- command. I have survival data set that observes individuals from age of 30 to a max age of 50. During this period a person can be promoted once (variable promo). This variable take 1 if a person gets promoted.

i used the following command initially to set the survival data-

command 1 - stset age, f(promo) id(id)

By default stata sets the origin time to be 0.

Since, i don't observe people before they are 30, I changed the st set command to the following:

command 2- stset age, id(staff_id) failure(promo) origin(time 30)

I compared the failure function using -sts list- after each different setting and it was quite different.

So my question is:
1. Why setting the origin significantly change the failure function?
2. I tried changing the earliest time of entry using en(time 30), while not changing the origin time it still produced the same failure functions as command 1. Why does stata still assume that origin time is zero?

Thanks alot.
Danula