Limits on the precision of the power calculations that derive from the approach outlined here include limits of the precision of estimation of the parameters whose estimation is required. Several of these parameters can be estimated based on substantial empirical data. These include the size of the genome or genomic segment under consideration, the sizes of the samples of disease and nondisease control subjects studied and the value for α desired. The frequency P [D] of the disease in the population under study is available from epidemiological studies. It is thus important that the samples for association genome scanning display characteristics similar to those of the populations in which disease probabilities were determined, so that estimates of P [D] are as accurate as possible.
