st: Stratified cox regression: How many indivduals contribute to the analysis

[Grethe Søndergaard <dkstatstata@gmail.com>]

Hi,

I am analysing my data using a stratified cox regression model. I use
a sibling statum variable, taking the same value for individuals who
are full siblings. The individuals in the data set have between 1 and
5 full siblings.

(Variables in the data set):
Person_ID
Father_ID
Mother_ID
Exposure
Outcome
Number_of_siblings
...

Only siblings who discordant on exposure and where at least one of
them experiences the outcome contribute to the analysis. Is there a
way to find out how many of the siblings in my data that contribute –
e.g. by using “expand”?

Thank you

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