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From | Roger Newson <r.newson@imperial.ac.uk> |
To | "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |
Subject | Re: st: McNemar's test with clustering |
Date | Mon, 26 Apr 2010 11:22:31 +0100 |
I will assume that you have a dataset with 1 observation per body side per twin, keyed by the variables -twinpair- (an ID number for twin pairs), -twinseq- (indicating whether the twin is the first or second twin and with values 1 or 2), and -side- (with values 1 for left and 2 for right). The outcome variable will be called -feature-, equal to 1 if a feature is present on that side of that twin in that pair, and equal to 0 if the feature is absent in that side of that twin of that pair. You could then type
somersd side feature, transf(z) tdist cluster(twinpair) funtype(vonmises)and -somersd- will give you a difference between the proportion of right sides with the feature and the proportion of left sides with the feature, with confidence intervals adjusted for the fact that we are sampling twin pairs from a population of twin pairs (instead of sampling twins from a population of twins or even sides from a population of sides).
I hope this helps. Let me know if you have any further queries. Best wishes Roger Roger B Newson BSc MSc DPhil Lecturer in Medical Statistics Respiratory Epidemiology and Public Health Group National Heart and Lung Institute Imperial College London Royal Brompton Campus Room 33, Emmanuel Kaye Building 1B Manresa Road London SW3 6LR UNITED KINGDOM Tel: +44 (0)20 7352 8121 ext 3381 Fax: +44 (0)20 7351 8322 Email: r.newson@imperial.ac.uk Web page: http://www.imperial.ac.uk/nhli/r.newson/ Departmental Web page: http://www1.imperial.ac.uk/medicine/about/divisions/nhli/respiration/popgenetics/reph/ Opinions expressed are those of the author, not of the institution. On 26/04/2010 02:39, Laura Gibbons wrote:
I'd like to do something like McNemar's test, -mcc-, where I'm comparing presence of two dichotomous traits in each person. [In this case, is a finding more common on the left side of the spine, compared to the right.] The problem is that the subjects are twins, in this analysis a nuisance parameter, but svyset or cluster(pair) are not options for mcc. For continuous outcomes I can get the equivalent of a paired t-test by computing the difference and then getting the p-values from the intercept in reg difference, cluster(pair) but I've not come up with anything along these lines either. Any guidance would be appreciated, thanks! -Laura ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Laura E. Gibbons, PhD General Internal Medicine, University of Washington Box 359780, Harborview Medical Center, 325 Ninth Ave, Seattle, WA 98104 phone: 206-744-1842, fax: 206-744-9917, Office address: 401 Broadway, Suite 5122 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/
* * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/