- The multi-rules procedure published by Westgard et. al. (1981)*, is used for Levey-Jennings control chart
to detect trends or shifts by examining individual values (to determine the status of the measuring system).
- These rules are based on σ and are hence calculated without regard to constant sample sizes.
* Westgard, J.O., Barry, P.L., and Hunt, M.R. (1981). A Multi-Rule Shewhart Chart for Quality Control in Clinical Chemistry.