Interference's are not restricted to the experimental levels. The region of values for which the alternate hypothesis is accepted. For a business or manufacturing process, the sigma value is a metric that indicates how well that process is performing. The higher the sigma value, the better. A defect is anything that results in customer dissatisfaction.
Sigma is a statistical unit of measure which reflects process capability.
Meaning no more than 3.4 parts per Million. Such a condition is most often evidenced on a control chart, i.e., a control chart which displays an absence of nonrandom variation. The application of statistical methods and procedures relative to a process and a given set of standards. That which is connected according to a scheme. All trademarks or product names mentioned herein are the property of their respective owners.