TDT Power calculator
Described in: 
Ferreira, Sham, Daly & Purcell (2007) Ascertainment through family history of disease often decreases 
the power of family-based association studies. Behav Genet, 37(4), 631-6. 
See the reference section for a brief description of input paramters and output statistics. 



Disease parameters


  k    Disease prevalence                    [0.0001 - 0.9999] 
  p    Allele frequency                      [0.0001 - 0.9999]
  Vq   Total locus variance                  [0 - 1]
  Va   Background additive genetic variance  [0 - 1]
  Vc   Shared environment variance           [0 - 1] 
 
         Dom 
         Add 
         Rec 
  Inheritance model 


Ascertainment parameters


  Number of families  
 
         1 
         2 
         3 
     N affected offspring per family required for selection
 
         No 
         Yes 
   Ascertain discordant parents?


Analysis and output options

 
         1 
         2 
         3 
     N affected offspring per family used for TDT (i.e. genotyped)
  Type-I error (alpha)
 
         Short 
         Long 
  Output format