An Evaluation of Percentile and Maximum Likelihood Estimators of Weibull Parameters

Two methods of estimating the three-parameter Weibull distribution were evaluated by computer simulation and field data comparison. Maximum likelihood estimators (MLB) with bias correction were calculated with the computer routine FITTER (Bailey 1974); percentlie estimators (PCT) were those proposed by Zanakis (1979). The MLB estimators had superior smaller bias and mean square error but larger variance than the PCT estimators. The MLB bias correction in FITTER increased the bias of parameter c, suggesting that for the three-parameter Weibull, the MLB estimators should be used without the correction. Comparisons of predicted percentages indicate that either MLB or PCT estimators, which are simpler to use, can model pine plantations equally well. Forest Sci. 31:260-268.