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


From   "Natarajan, Raj" <Raj.Natarajan@roswellpark.org>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: RE: RE: selecting random samples and run a simulation
Date   Fri, 13 Jul 2007 11:33:50 -0400

 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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