Question: A local supermarket knows that, on average, it receives 12 customer complaints a day about poor quality service, damaged goods and so on. The standard deviation around this average is 5. The supermarket manager wants to set up a control chart to monitor this aspect of performance, with results compiled for each two-week period (the store is open seven days a week).
Calculate warning and action limits for this situation.
The first seven sets of results are:
13.4, 11.3, 14.2, 12.5, 11.1, 10.7, 9.5
Comment on the store's performance in this context.