Bookmark and Share

Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at statalist.org.


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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
 
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/faqs/resources/statalist-faq/
*   http://www.ats.ucla.edu/stat/stata/


© Copyright 1996–2018 StataCorp LLC   |   Terms of use   |   Privacy   |   Contact us   |   Site index