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Activity Number:
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473
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Type:
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Contributed
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Date/Time:
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Wednesday, August 5, 2009 : 10:30 AM to 12:20 PM
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Sponsor:
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Biometrics Section
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| Abstract - #305698 |
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Title:
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Power of Genetic Association Studies with Fixed and Random Genotype Frequencies
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Author(s):
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Julia Kozlitina*+ and William Schucany
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Companies:
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The University of Texas Southwestern Medical Center at Dallas and Southern Methodist University
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Address:
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5323 Harry Hines Blvd., Dallas, TX, 75235-8591,
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Keywords:
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Power ; Random ; Genetic ; Association
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Abstract:
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When estimating the power of genetic association studies, the allele frequencies are often assumed to be known, and the numbers of individuals with each genotype are set equal to their expectations under Hardy-Weinberg (HW) equilibrium. Ambrosius et al. (2004) showed that treating the genotype counts as fixed rather than random can lead to inflated power expectations. For a given allele frequency, they proposed averaging power estimates over the distribution of trinomial sample counts to get a more accurate estimate of power. We analyze their method and find that although the approach of fixing genotype counts does lead to an upward bias in estimated power, the magnitude of bias decreases dramatically with sample size, and is negligible for large N. Therefore for moderately large studies (N>200) estimating power from genotypes that are HW proportions may be a reasonable approach.
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