The time to be seated at a popular restaurant is of importance. Samples of five randomly selected customers are chosen and their average and range (in minutes) are calculated. After 30 such samples, the summary data values are

(a) Find the - and Ä-chart control limits.
(b) Find the 1σ and 2σ - chart limits.
(c) The manager has found that customers usually leave if they are informed of an estimated waiting time of over 10.5 minutes. What fraction of customers will this restaurant lose? Assume a normal distribution of waiting times.
TABLE 7-19

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