Re: st: comparing results from cluster and stratified analysis

[Grethe Søndergaard <dkstatstata@gmail.com>]

Hi Steve,

Thank you for your response and for advises. They seem to work right
the way I wanted.

Kind regards Grethe

2010/12/30 Steven Samuels <sjsamuels@gmail.com>:
> --
> You can certainly compare the results, but it won't hurt to do the
> non-stratified  analysis on the reduced data set.
> A formal test of the effect of family would require a bootstrap or a test of
> the Gamma parameter in the random effects frailty model; but the Gamma
> assumption is quite restrictive.
>
> Perhaps you misunderstand the role of clusters. The  -vce()- options,
> including -vce(cluster ), affect only the estimation of standard errors. You
> could use any -vce()- option for a non-stratified analysis or  stratified
> analysis. So, in the stratified analysis, family could be both a cluster and
> a stratum variable.
>
> To drop all groups with tied values for covariates x1 x2 x3 x4:.
>
> *********First Principles********************
> bys group: gen gc1= _N
> bys group x1 x2 x3 x4: drop if _N==gc1
> *********Simplest********************
> duplicates drop group x1 x2 x3 x4
>
>
>
> Steve
>
> Steven J. Samuels
> sjsamuels@gmail.com
> 18 Cantine's Island
> Saugerties NY 12477
> USA
> Voice: 845-246-0774
> Fax:    206-202-4783
>
> On Dec 29, 2010, at 4:30 AM, Grethe Søndergaard wrote:
>
> 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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