Abstract
The method of estimating three points used in PERT is based on the condition of the standard deviation of Beta-distribution as one-sixth of the difference between the pessimistic and optimistic estimates because PERT is prepared for the specific project. However, for the purpose of setting the department goal and selecting the plans of systems improvement in a business firm, a generalized method, proposed in Journal of JIMA, Vol.26,No.1,1975 by KOGURE and AKIBA, is suited in which the variance is also estimated by estimator's degree of confidence. In the presence paper, the quantitative relations between the standard deviation of Beta-distribution and estimator's degree of confidence are revealed by experimental research.
