What does a control chart measure over time?

A control chart is a statistical tool used in quality control to monitor and analyze the stability of a process over time. It plots data points in time order and includes control limits, which help determine if a process is in a state of statistical control. When using a control chart, the primary objective is to assess process stability by observing variations within the process.

By identifying any patterns or trends in the plotted data, quality engineers can determine whether a process is consistently producing results that fall within predetermined limits or if there are signs of instability that may require intervention or adjustments. Stable processes are crucial because they indicate that the outcome is predictable and manageable, leading to improved quality and efficiency.

In contrast, customer satisfaction, product performance, and cost efficiency are related but do not directly measure the stability of the process itself. Customer satisfaction might be influenced by stable processes but is not a measure of process control. Similarly, product performance can be affected by the process but does not specifically indicate stability. Cost efficiency, while important to assess overall performance, is also not a direct measure of process stability. Thus, the focus of a control chart is centered on monitoring and achieving stability within a given process.