Detection of inbreeding effects by the chi-square test on genotypic and phenotypic frequencies.

The problem of detection of inbreeding effects by the chi-square goodness-of-fit test is investigated. The noncentrality parameter of the limiting chi-square distribution is considered as a function of the inbreeding coefficient in two models: (1) a gene locus with m codominant alleles and (2) the generalized ABO model. Previous results by Ward and Sing and by Chakraborty and Rao were based on inadequate statistical reasoning. In the first model, the resulting noncentrality parameter is identical with that found by Ward and Sing. For the second model, the limiting noncentrality parameter is found to be zero.