st: comparing results from cluster and stratified analysis

[Grethe Søndergaard <dkstatstata@gmail.com>]

Hi,

I am analysing my data in two steps, using cox-regression analysis in
both. My data set consists of siblings from different families.

First I am using a standard cox-regression analysis, where I include a
cluster term to take into account that some of the persons in my data
are related.
Next, I am using using a stratified cox-regression analysis, where I
use a “sibling” stratum variable, to stratify my analysis on persons
who are siblings.

I want to compare the results from the cluster analysis with the
result from the stratified analysis – and know I am having doubts of
whether I am doing this the right way. In the stratified analysis,
only siblings who are discordant on both exposure and outcome will
contribute to the analysis. However, in the cluster analysis all
siblings in the data set will contribute (as far I understand). But
can you actually compare these results?

If no - Is there a way to delete all the individuals, who are not
discordant on exposure and outcome with at least one of his/her
siblings, before running the cluster analysis?

Grethe

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