What does the X Bar chart plot?

The X Bar chart is a crucial tool used in statistical process control (SPC) to monitor and analyze the average values of subgroups over time. It is specifically designed to track the mean of a set of measurements taken from a process at different times or under varying conditions. By plotting these averages, the X Bar chart helps to identify trends, shifts, and variations in the process mean, allowing for better understanding and control of process stability.

In this context, the chart provides visual feedback on the process performance, revealing whether the process is consistently within the desired control limits. This ability to monitor the average effectively helps manufacturers make informed decisions about maintaining quality and reducing variability in their operations.