Re: st: logistic regression

["meena khan" <meena_25@hotmail.com>]

Hi Neil,

I'm trying to do an allele-wise analysis, the genotype analysis was as you 
said where the genotype is recoded. It is not quite a matched case control: 
there is not a case for each control where the outcome alternates like this:

              x              outcome
1             1                  1
1             2                  0
2             1                  1
2             1                  0
3             1                  1
3             2                  0

In my dataset, the outcome remains the same for each ID row (as it is the 
same person) they just have a 2 different alleles which are different for 
each person which is what i am testing, so:

ID          SNP              outcome
1             1                  1
1             2                  1
2             1                  0
2             1                  0
3             1                  0
3             2                  0

I have slightly different 95% confidence intervals when i do normal logistic 
regression and when i introduce the cluster (ID) option, so there is a 
difference in the 2 methods. Do you know why this is and which is the better 
model to use? Thanks

Meena



> From: "Neil Shephard" <nshephard@gmail.com>
> Reply-To: statalist@hsphsun2.harvard.edu
> To: statalist@hsphsun2.harvard.edu
> Subject: Re: st: logistic regression
> Date: Mon, 12 Mar 2007 15:35:06 +0000
>
> On 3/12/07, Neil Shephard <nshephard@gmail.com> wrote:
> > The logistic cluster option would be appropriate if your cases and
> > controls have been matched on an additional trait such as age or sex
> > (in which case you would add -, cluster(age)- to the above command).
> > More on this is given in the book Clayton & Hills (1993) "Statistical
> > Models in Epidemiology" OUP (I don't have it to hand, but I think its
> > chapter 29).
> Further reflection on what I wrote earlier (and reading the -man-
> pages) indicates that my above suggestion as to the use of the
> -cluster()- option is completely wrong.
>
> If you do have matched cases and controls then you would need an
> additional column which indicates which group individuals belong to.
> Thus in your given data example if person 1 is matched to person 2
> then there should be a additional column that indicates this as group
> 1.  (If person 3 and 4 are matched then they would form group 2 and so
> on).
>
> You then specify the variable that indicates which group pairs belong
> to in the -cluster()- option.
>
> Apologies for any confusion I've caused,
>
> Neil
> --
> "Every great advance in natural knowledge has involved the absolute
> rejection of authority."  - Thomas H. Huxley
>
> Email - nshephard@gmail.com / neilshep@cyllene.uwa.edu.au
> Website - http://slack.ser.man.ac.uk/
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