Applied Machines produces large test equipment for integrated circuits. The machines are made to order, so the production rate varies from month to month.

Before shipping, each machine is subject to extensive testing. Based on the tests the machine is either passed or sent back for rework. During the past 20 months the firm has had to rework the following numbers of machines:

Number Number Number Number Month Produced Reworked Month Produced Reworked 1 23 3 11 17 3 2 28 3 12 4 0 3 16 1 13 14 2 4 6 0 14 0 0 5 41 2 15 18 6 6 32 4 16 0 0 7 29 5 17 33 4 8 19 2 18 46 5 9 12 1 19 21 7 10 7 1 20 29 7 Determine if the process was in control for the 20-month period using a standardized version of the p chart. Assume three-sigma limits for the control chart.

(Hint: Do you actually have 20 months of data?)