Posted by
Paul Oosterveld on
Nov 12, 2012; 2:43pm
URL: http://spssx-discussion.165.s1.nabble.com/Random-sample-matched-on-variables-tp5716152p5716156.html
Koen,
In this situation I would rather weight on the propensity score than match
on these (the propensitie can be obtained by logistic regression). In that
approach all data in the control group could be included, while having the
demographic frequencies characteristics of the (combined) intervention
groups. For turning this problem into a script, frequency distributions of
the demographics in the three groups would be needed. If this will work
depends on the discrepancies between the groups.
Regards,
Paul Oosterveld.
On Sun, 11 Nov 2012 05:55:17 -0800, Bruce Weaver <
[hidden email]>
wrote:
>From what you've said, it /sounds/ as if N=65 for control versus 25-30 for
>the other two groups. That is not what I would describe as a large
>discrepancy in sample sizes.
>
>What type of study design is it? (E.g., see
>
http://www.med.uottawa.ca/sim/data/Study_Designs_e.htm.)
>
>What kinds of outcome (dependent) variables do you have, and what types of
>models are you using?
>
>
>
>Koen N wrote
>> Dear more experienced than me SPSS users,
>>
>> I'm currently working on a research project in which I've hit a wall. I
>> have three groups which I want to compare on a number of analysis. One of
>> these groups is much too large compared to the other groups. This much
too
>> large group is a control group. The other two groups are comprised of a
>> rare demographic. As of such, I want to drop my control group of 65 down
>> to 25-30 while matching them on certain demographic variables (namely
age,
>> IQ and education). The other two groups don't differ significantly from
>> one another on the mean of these variables. My control group does differ
>> sognificantly. I want my control group sample to be within the same range
>> of the means of my other two groups.
>>
>> Obviously (otherwise I wouldn't be posting), I am completely lost as to
>> how to do this. I assume I'll be using the syntax, but I am unsure what
>> commands I should be using. I've searched around and found some similar
>> cases as mine, except they wanted to take a random sample based on
>> propensity scores (which I don't believe works for me) or they wanted to
>> take a sample out of two groups (while I want a sample out of one).
>>
>> If anyone could assist me, I would be very grateful. Thanks for your
time!
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