A note on power approximations for the transmission/disequilibrium test

Am J Hum Genet. 1999 Apr;64(4):1177-85. doi: 10.1086/302334.


The transmission/disequilibrium test (TDT) is a popular method for detection of the genetic basis of a disease. Investigators planning such studies require computation of sample size and power, allowing for a general genetic model. Here, a rigorous method is presented for obtaining the power approximations of the TDT for samples consisting of families with either a single affected child or affected sib pairs. Power calculations based on simulation show that these approximations are quite precise. By this method, it is also shown that a previously published power approximation of the TDT is erroneous.

MeSH terms

  • Alleles
  • Bipolar Disorder / genetics
  • Chromosome Mapping / methods
  • Chromosome Mapping / statistics & numerical data*
  • Computer Simulation
  • Female
  • Gene Frequency
  • Genetic Predisposition to Disease / genetics
  • Genotype
  • Humans
  • Likelihood Functions
  • Linkage Disequilibrium / genetics*
  • Male
  • Matched-Pair Analysis
  • Mathematics
  • Models, Genetic
  • Nuclear Family
  • Odds Ratio
  • Sample Size
  • Tryptophan Hydroxylase / genetics


  • Tryptophan Hydroxylase