The owner of a dry cleaning business, in an effort to measure the quality of the services provided, would like to study the number of dry-cleaned items that are returned for rework per day. Records were kept for four weeks (Monday to Saturday) with the following results (read across from left to right):
4 6 3 7 6 8 6 4 8 6 5 12
5 8 3 4 10 9 6 5 8 6 7 9
(a) Define the random variable of interest and state the distribution you would expect this random variable to have.
(b) Set up the appropriate control chart(s) to monitor the random variable of interest.
(c) Suppose that the previous long run average for the number of items returned was 5 per day. Recalculate the control limits and evaluate the results in light of this information.