Who is credited with the use of sigma levels as a measure of quality?

Walter A. Shewhart is credited with the use of sigma levels as a measure of quality because he introduced the concept of control charts and variability in the manufacturing process. His work laid the foundation for statistical quality control, where he emphasized the importance of understanding variability to improve process quality. The sigma level, which quantifies the number of standard deviations that a process mean is from the nearest specification limit, derives from Shewhart's principles in measuring and interpreting quality performance. This framework eventually evolved into the Six Sigma methodology, which uses sigma levels to indicate the capability of processes concerning defects and quality.

Other figures mentioned have made significant contributions to quality management, but they did not specifically originate the sigma level concept. Deming focused on continuous improvement and the System of Profound Knowledge, while Philip Crosby is well-known for promoting the idea of “zero defects.” Their contributions are invaluable to the quality movement, yet they do not specifically pertain to the genesis of sigma levels in measurement.