Part 4: Control Charting

Background:

Based on their quality control work so far, the VivosysQ project team believes that they can significantly increase customer satisfaction by reducing hold times for telephone callers seeking technical assistance. They decide to construct a control chart to see the past performance of this variable and track future performance.

The Vivosys computer system records the hold time for each call. Asking the computer for the average hold times for each day during the past months yields the following data: