Statistics for Business: Decision Making and Analysis, 3rd Edition

Case Summary

Modern packaging produces variation among individual items. With a few assumptions, we can model this variation using a normal model that allows us to anticipate differences from item to item. The normal model works because sums of independent random variables, whether counts or measured values to many digits of accuracy, eventually have a normal distribution. The bell curve appears because of the variety of ways to get sums that are near the expected value of the total. We can exploit normality for many things, including monitoring modern automated machinery.