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Re: st: RE: RE: RE: selecting random samples and run a simulation


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: RE: RE: selecting random samples and run a simulation
Date   Fri, 13 Jul 2007 22:55:21 +0100 (BST)

my bad, but that is easily mended:
set obs 1000
gen control_case = cond(_n>500, /* 
                       */invnorm(uniform())+1.4, /*
                       */invnorm(uniform()))
gen status = _n >500


--- "Natarajan, Raj" <Raj.Natarajan@roswellpark.org> wrote:

>  Thanks for the suggestion Maarten. The cases have different means as
> you could see from my example.
> 
> ________________________________
> 
> From: owner-statalist@hsphsun2.harvard.edu on behalf of Maarten Buis
> Sent: Fri 7/13/2007 10:59 AM
> To: statalist@hsphsun2.harvard.edu
> Subject: st: RE: RE: selecting random samples and run a simulation
> 
> 
> 
> As both the controls and the cases are random draws from a normal
> distribution and the two are uncorrelated you can just draw 1000
> random numbers from a normal distribution and call the first 500
> controls and the last 500 cases.
> 
> set obs 1000
> gen control_case = invnorm(uniform())
> gen status = _n >500
> 
> Hope this helps,
> Maarten
> 
> -----------------------------------------
> Maarten L. Buis
> Department of Social Research Methodology
> Vrije Universiteit Amsterdam
> Boelelaan 1081
> 1081 HV Amsterdam
> The Netherlands
> 
> visiting address:
> Buitenveldertselaan 3 (Metropolitan), room Z434
> 
> +31 20 5986715
> 
> http://home.fsw.vu.nl/m.buis/
> -----------------------------------------
> 
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu]On Behalf Of Natarajan,
> Raj
> Sent: vrijdag 13 juli 2007 16:47
> To: statalist@hsphsun2.harvard.edu
> Subject: st: RE: selecting random samples and run a simulation
> 
> I sent this e-mail yesterday but did not get any response. So I am
> resending hoiping it will come out.
> 
> ________________________________
> 
> From: Natarajan, Raj
> Sent: Thu 7/12/2007 8:26 AM
> To: statalist@hsphsun2.harvard.edu
> Subject: selecting random samples and run a simulation
> 
> 
> 
> I would like to draw a random sample of 500 controls and 500 cases
> and calculate the odds ratio; repeat the process for 1000 times.
> 
> Example: (draw random sample)
> 
> matrix means=(0, 1.4)
> 
> matrix stdev = (1, 1)
> 
> draw norm control case, n(500) m (means) sds(stdev)
> 
> 
> the outcome for the first 5 observations  will look like this:
> 
>   control          case
> 
>  -1.315189      .1754738
> 
> -.6195259       -.4363556
> 
> -1.18018        .2124426
> 
> -.2960889       -.5825416
> 
> .4534519        -.1245893
> 
> PROBLEM: I would like the outcomes for controls and cases to be in
> one column and create a new variable called "status" which is 0 for
> control and 1 for case.
> 
> Control_case        status
> 
> -1.315189               0
> 
> -.6195259               0
> 
> -1.18018                0
> 
> -.2960889               0
> 
> .4534519                0
> 
> .1754738                1
> 
> -.4363556               1
> 
> .2124426                1
> 
> -.5825416               1
> 
> -.1245893               1
> 
> I have to run the logistic regression to calculate the odds ratios;
> and repeat the process with different variances.
> 
> I would like to know how to make the outcomes arranged in one column
> with the creation of the variables "control_case" and "status".
> 
> Thank you for any suggestion.
> 
> Raj
> 
> 
> 
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-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------


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