What is a control chart and when would you use it?

• A. A tool to estimate costs.
• B. A statistical tool to monitor process performance over time and detect variability; used in quality management.
• C. A method to allocate resources.
• D. A chart showing network dependencies.

Answer: (B)

A control chart is a statistical tool to monitor how a process performs over time and detect variability; it is used in quality management. It plots measured values in sequence with a center line showing the process average and upper and lower control limits that define the expected range of normal variation. When the process remains in control, data points bounce around the center without nonrandom patterns. If you see points outside the control limits or patterns such as runs, trends, or cycles, that signals a potential assignable cause that should be investigated. Use it to keep a process steady, track performance over time, and determine whether changes lead to real improvements. It’s not about estimating costs, allocating resources, or mapping network dependencies, which are separate topics.