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Power of the Classical Twin Design Revisited

Published online by Cambridge University Press:  21 February 2012

Peter M. Visscher
Peter M. Visscher*
Affiliation:
School of Biological Sciences, University of Edinburgh, United Kingdom. [email protected]
*
*Address for correspondence: Peter M. Visscher, School of Biological Sciences, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, Scotland, UK.

Abstract

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Statistical power of the classical twin design was revisited. The approximate sampling variances of a least-squares estimate of the heritability in a univariate analysis and estimate of the genetic correlation coefficient in a bivariate analysis were derived analytically for the ACE model. Statistical power to detect additive genetic variation under the ACE model was derived analytically for least-squares, goodness-of-fit and maximum likelihood-based test statistics. The noncentrality parameter for the likelihood ratio test statistic is shown to be a simple function of the MZ and DZ intraclass correlation coefficients and the proportion of MZ and DZ twin pairs in the sample. All theoretical results were validated using simulation. The derived expressions can be used to calculate power of the classical twin design in a simple and rapid manner.

Type
Articles
Information
Twin Research and Human Genetics , Volume 7 , Issue 5 , 01 October 2004 , pp. 505 - 512
Copyright
Copyright © Cambridge University Press 2004