
28 Six Sigma Case Studies with Minitab
®
the hamburgers have fat content with a standard deviation that is lower than
2.89 grams. Inasmuch as 2.89 grams is much greater than the assumption of
1 gram, the operations manager considers this also a serious issue.
Before proceeding to the improve phase, the operations manager wishes
to check how many of the customers are dissatised. To this end, he ran-
domly selects 1,000 customers who bought hamburgers and nds that 83 of
them are dissatised with the food quality. He then proceeds to construct a
condence interval for the proportion of all customers who are dissatised.
Figure3.11 shows how to select ...