AN EMPIRICAL-INVESTIGATION OF THE 2-MOMENT APPROXIMATION FOR PRODUCTION LINES

Since Muth (1973) it has generally been accepted that the throughput o f production lines with variable processing times depends primarily on the first two moments of the processing time distribution. However, s everal recent studies have suggested that differences in higher moment s may lead to significant differences in throughput. In order to shed light on this question, we examine the applicability of the two-moment approximation over a variety of types of lines (both serial and assem bly) and a variety of processing time distributions. We find significa nt differences in throughput (on the order of 5%) even among commonly used probability distributions, and large differences (as large as 28% ) among highly skewed and kurtotic distributions. We also find that th e differences among distributions generally increase with the number o f stations in the line and with the coefficient of variation of proces sing times.