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?

Statistical process control (SPC) is a data-driven process that uses statistical methods to monitor and control the quality of a production process. The goal of SPC is to ensure that the process is stable, consistent with customer requirements, and not drifting or changing in an unexplainable manner. 

SPC is commonly used in manufacturing or production processes to measure how consistently a product performs according to its design specifications. Some of th