USING THE BETA-BINOMIAL DISTRIBUTION TO CHARACTERIZE FOREST HEALTH

The beta-binomial distribution is suggested as a model for describing and analyzing the dichotomous data obtained from programs monitoring t he health of forests in the United States. Maximum likelihood estimati on of the parameters is given as well as asymptotic likelihood ratio t ests. The procedure is illustrated with data on dogwood anthracnose in fection (caused by Discula destructiva) in the southeastern United Sta tes. The parameter estimates have important biological interpretation, and tests of hypotheses are more meaningful than traditional statisti cal analyses. The value of a modeling approach to dichotomous data ana lysis is emphasized.