What does it indicate if a sample of parts has a mean measurement outside of the control limits?

When a sample of parts has a mean measurement that falls outside the control limits, it indicates that the process is out of control. Control limits are statistical boundaries set based on the natural variation within a process. These limits are established using data from a stable process and define the expected range of variation.

When the mean measurement exceeds these limits, it signals that there's a significant variation that cannot be attributed to the inherent randomness of the process. This could be due to assignable causes or issues affecting the process that need to be identified and addressed. Thus, a mean outside control limits typically requires immediate attention to investigate and rectify any potential problems contributing to this out-of-control situation.