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08-13-2014 04:35 PM

Hi All:

I am working on a logistic regression-- binary outcome. The 1 (or the event) has a sample size of 600, while the 0 (non-event) has a sample size of 8000.

How do I extract a random sample of 600 of the non-event? It seems like proc suveyselect only lets me take a random sample of all participants, not just those who fall in the non-event.

Thanks so much!

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Posted in reply to murugan

08-13-2014 04:54 PM

On the input dataset name use the where option to select input records only for specific values. This completely subsets the data. The selection probability and weights will only work for that subset so be careful.

proc surveyselect data=lib.have (where=(eventvariable = 0)) ....

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Posted in reply to ballardw

08-15-2014 01:12 PM

This code is not working. I keep getting an error message that says that my use of the where statement is incorrect.

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Posted in reply to murugan

08-15-2014 02:48 PM

Post the code you're submitting

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Posted in reply to murugan

08-15-2014 02:52 PM

Hi,

Seems like trying to make a dataset containing equal number of event and non-event cases. Try this to get the desired sample dataset.

data sample;

set have;

if y=1 or (y=0 and ranuni(1234)<0.075) then output; /* Suppose y is the event variable */

run;

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Posted in reply to stat_sas

08-15-2014 03:08 PM

When I used the code that you suggested, I got: data set has 0 observations and 1 variable.

I am trying to make a dataset containing an equal number of event and non-event cases.

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Posted in reply to stat_sas

08-15-2014 03:09 PM

Thank you for all of your help!

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Posted in reply to murugan

08-15-2014 04:14 PM

If you had clearly stated your need earlier then STRATA in survey select with event and nonevent sample sizes specified would have worked.