BBD-COMPUTER SOFTWARE FOR FITTING THE BETA-BINOMIAL DISTRIBUTION TO DISEASE INCIDENCE DATA

A software program for DOS-based personal computers was developed to fit the beta-binomial distribution to the frequency of incidence of disease. The beta-binomial is a discrete distribution, which is appropriate for describing aggregated or clustered binary data such as incidence. Variance-ratio and C(alpha) tests are performed to determine if there is evidence that incidence is aggregated. The program then calculates distribution parameters and their standard errors using a maximum likelihood procedure, determines the expected values of the distribution, and calculates a chi-square goodness-of-fit test. For comparison purposes, the program fits the binomial distribution to the same data. The software and a detailed user's manual are available free from either author.