A Nationwide Parcel Delivery Service Keeps Track of the Number $\bar { X }$

Multiple Choice

A nationwide parcel delivery service keeps track of the number of late deliveries (more than 30 minutes past the time promised to clients) per day. They plan on using a control chart to plot their results. Which type of control chart(s) would you recommend?

A) $\bar { X }$ - and R-charts
B) p-charts
C) c-charts
D) $\bar { X }$ -, but not R-charts
E) both p- and c-charts