What happens to the capability of a process if there is a decrease in u-bar?

When considering the capability of a process in relation to the mean (u-bar), a decrease in the mean typically indicates a shift in the process toward the target or desired performance level, assuming that the process variability remains constant. This shift leads to improved capability, as the process is producing results that are closer to specification limits or target values.

In quality management, process capability is often assessed using indices like Cp and Cpk. A decrease in u-bar could enhance the Cpk index if the process becomes more centered within the specification limits, thereby making the process more capable of producing output that meets quality standards consistently.

Understanding capability also involves considering how a process's performance improves when it is more aligned with customer requirements or specifications. Therefore, a decrease in u-bar, reflecting a more favorable positioning of the process relative to its specification limits, is typically viewed as an improvement in capability.