Abstract
Statistical analyses of occupational accidents considering the variance of accident frequency rate were carried out. Emphasis was placed on the probabilistic and statistical analyses to clarify the frequency distribution of the number of accident occurrences and the time interval between accidents. From accident investigations, it was found that both the Poisson and negative binomial distributions agreed well with many actual accident cases. The frequency distribution of each of the number of accident occurrences and the time interval between accidents can be represented as a mixture of the probability distribution of the accident frequency rate and the corresponding probability distribution function. These mixing ultimately gives a negative binomial distribution for the number of accident frequency and a composite gamma distribution for the time intervals between accidents. Parameters of the distribution of accident frequency rate can be determined from actual accident data. Where such data is insufficient, the Bayesian statistical inference scheme can be employed as an alternative method to estimate the parameters of distribution.
