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The isonymy and pedigree methods of estimating average in­breeding in a population were applied to different types of samples drawn from the records of a Mennonite congregation. The degree of concordance between the isonymy and pedigree derived inbreeding coefficients varied with the nature of the samples used. Concordance was highest (near 100%) when the characteristics of the samples were closely matched. The results indicate that sampling procedures may have contributed to low concordance observed in previous studies. The pedigree and isonymy methods differ in (1) the nature of the inbreeding coefficient obtained, and (2) the samples to which they apply. The isonymy formula provides the theoretical inbreeding coefficient of the offspring of the mating pairs sampled assuming that all couples have equal numbers of offspring. The pedigree method provides the actual inbreeding coefficient of the individuals sampled. When the funda­mental sampling differences between the two methods are controlled, con­cordance may improve.