The three-sigma rule, also known as the 68-95-99.7 rule, is a statistical rule that states that approximately 68% of all measurements lie within one standard deviation of the mean, about 95% within two standard deviations, and about 99.7% within three standard deviations.
The three-sigma rule is often applied in industry to determine whether a process or product in manufacturing is within expected tolerance limits. If a process or product is outside of three standard deviations, it is assumed that there is a problem and measures are taken to identify and resolve the issue.
The three-sigma rule is a useful tool for quality control and testing in industrial manufacturing. It can help to detect process problems early, before they lead to serious quality problems or failures. The application of the three-sigma rule can also help to reduce production costs by helping to reduce scrap and errors.
It is important to note that the three-sigma rule is a statistical rule and does not account for all factors that may affect measurements. Other factors such as measurement errors, sensor errors, environmental conditions, and operator errors can also affect measurement accuracy and should be considered when interpreting measurement results.