An Internet book retailer promises to ship all customer orders within 24 to 36 hours of receiving an order at its web site. Actual shipment data for all computers shipped during the past month showed that the average delivery time was 30 hours, and the standard deviation was 4 hours.
(a) Is the company delivering Six Sigma quality to its customers?
(b) If not, then how much should the standard deviation of the process be reduced to get Six Sigma quality?