Monitoring System Performance: Frito-Lays uses statistical process control techniques to monitor the process used to produce Ruffles Potato Chips. One dimension of quality that consumers value is the proportion of broken chips. As it turns out, because of the nature of the product and the process used to produce Ruffles, the proportion of broken chips bagged is 0.10, which is well below the industry average. That is, when there are just common causes present, only 10 percent of Ruffles chips are broken (and Frito-Lays would like to keep it that way).

To make sure that assignable causes do not degrade their process, Frito-Lays is planning to take samples of 50 chips from random bags ready for shipment, count the number of broken chips and plot the resulting proportion of broken chips on a p-chart.

a. What would be the upper control limit of the p-chart?

b. What would be the lower control limit of the p-chart?

c. If the proportion of broken chips in the first sample were p=.12, is the process in control? (i.e., Can the variation be attributed to common causes?) Yes or no?