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st: Optimal ratio of sample sizes in two sample t test
From
Douglas McKee <[email protected]>
To
[email protected]
Subject
st: Optimal ratio of sample sizes in two sample t test
Date
Mon, 7 Jan 2013 14:50:40 -0500
Hi all,
Suppose I'm trying to choose the sample sizes for a study where I have two populations that are equally costly to sample. If I know the standard deviations of each group, I can use sampsi to compute the n's when I specify effect size, alpha and desired power. But suppose one sample has a low variance and the other has a high variance. Doesn't this mean I should sample more from the high variance group? Is there a way to make Stata tell me the optimal n1/n2 ratio? Or should I write a wrapper around sampsi that tries a variety of ratios and tells me which one yields the smallest n1+n2?
Thanks very much,
Doug
---------------
Douglas McKee
Associate Chair and Lecturer, Economics
Lecturer, School of Medicine
Yale University
[email protected]
http://www.econ.yale.edu/~dm529
310-266-2438
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