(1) To estimate the power of testing for linkage using an affected sib
pair design, as a function of the recurrence risk ratios. We will use
analytical power formulae as implemented in R. These are based on a
Mathematica notebook created by Martin Farrall. (2) To examine how the
power of the transmission disequilibrium test (TDT) depends on the disease
allele frequency, the marker allele frequency, the strength of the linkage
disequilibrium, and the magnitude of the genetic effect. 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.