Choice of ascertainment model I. Discrimination between single-proband models by means of birth order data.

A statistical method for choosing between ascertainment models for human family data has been constructed. The families are assumed to have been ascertained through a single proband each and the birth number of the proband among the affected children is recorded. If the proband is the eldest affected child in each family the so-called complete ascertainment model has to be used. If each affected child has the same probability of being the proband, the so-called single ascertainment model should be used. In intermediate cases a third ascertainment model should be used.