ptdt: Power for a TDT design

In powerpkg: Power Analyses for the Affected Sib Pair and the TDT Design

Power for a TDT design

Description

Function to compute power for a TDT design using formulae from Abel and Muller-Myhsok (1998) Am J Hum Genet 63:664-667

Usage

ptdt(g, q, m, ld, nfam, alpha)

Arguments

g	the genotype risk ratio for the susceptibility gene.
q	the susceptibility allele frequency
m	the frequency of the marker allele in linkage disequilibrium with the susceptibility allele.
ld	the strength ofthe linkage disequilibrium between marker and susceptibility allele, on a scale of 0 to 1.
nfam	the number of families.
alpha	the significance level of the test.

Details

We will use an R program that implements the power formulae of Abel and Muller-Myhsok (1998). These formulae allow one to quickly compute power of the TDT approach under a variety of different conditions. This R program was modeled on Martin Farrall's Mathematica notebook.

The power computations here use a simple genetic model with several aspects: (1) The disease locus has two alleles, A and a, with allele frequencies q and 1-q. The risk of disease follows a multiplicative model with genotype relative risks of g and g*g for the A/a and A/A subjects. (2) There is a perfectly linked marker with two alleles, with allele frequencies m and 1-m.

Value

power

power of the statistical test under the chosen conditions.

Note

This R program was modeled on Martin Farrall's Mathematica notebook.

Author(s)

Daniel E. Weeks

References

Abel L, Muller-Myhsok B. Maximum-likelihood expression of the transmission/disequilibrium test and power considerations. Am J Hum Genet. 1998 Aug;63(2):664-7.

Chen WM, Deng HW. A general and accurate approach for computing the statistical power of the transmission disequilibrium test for complex disease genes. Genet Epidemiol. 2001 Jul;21(1):53-67.

Iles MM. On calculating the power of a TDT study–comparison of methods. Ann Hum Genet. 2002 Jul;66(Pt 4):323-8.

Purcell S, Cherny SS, Sham PC. Genetic Power Calculator: design of linkage and association genetic mapping studies of complex traits. Bioinformatics. 2003 Jan;19(1):149-50.

See Also

plotNtdt, ntdt.q, ntdt

Examples

ptdt(q=0.15,m=0.25,ld=0.45,g=2.5,alpha = 0.05,nfam=300)
ptdt(q=0.15,m=0.25,ld=0.45,g=2.5,alpha = 0.05,nfam=400)

powerpkg documentation built on May 20, 2022, 1:09 a.m.