Test equality of adjusted survival functions

[Dan Smith]

Hello guys. I have a table similar to this:

id	power	category	time
1	35	A	8
2	50	A	34
3	75	B	17
4	50	A	11
5	60	B	50

After setting my survival data with:

sts time

I want to compare the 2 survival functions stratified for category = A and category = B, adjusted for Power =45

I can do it grafically, typing:

generate power45 = power–45

sts graph, strata(category) adjustfor(power45)

Or, as an alternative:

sts graph, by(category) adjustfor(power45)

My question now is: how can I perform a test on the equality of these 2 adjusted survival functions for know if they are statistically equal or not?
I can't figure it out, I'm pretty sure sts test can't help...

Thank you

[Dan Smith]

Anyone?

[Svend Juul]

You can use, for example, Cox regression to test the related hypothesis that the hazard ratio (A:B) is 1 - assuming that category is coded 1 for A, 0 for B:

stcox category power45

Svend