
33Confidence Intervals to Assess Variation in Fat Content
output shown in Figure3.17, the upper bound is 0.492 gram for the standard
deviation (given by the chi-square method). This means that 95% of the ham-
burgers have fat content with a standard deviation that is lower than 0.492
gram. Because 0.492 gram is less than the assumption of 1 gram, it is evident
that the process has improved with respect to the standard deviation as well.
One can also simulate condence intervals using Minitab
®
. The operations
manager wishes to perform the simulation for 10 normally distributed sam-
ples with a sample size of 20 hamburgers. Doing what is shown i