Alternative Factors for Control Chart Construction

This working paper series is intended to facilitate discussion and encourage the exchange of ideas. Inclusion here does not preclude publication elsewhere. It is the original work of the author(s) and subject to copyright regulations. ABSTRACT We believe that conflicting decision signals resulting from examining Shewhart Mean and Variability Control Charts produce undesirable consequences. Therefore, we construct " three-sigma " control charts by alternative methods to avoid problems associated with Mean and Variability Charts yielding different signals. We suggest adjusting control limits for range (R) and standard deviation charts using mean charts as the criterion. We provide new reference tables with concordant values for factors used to construct these control charts. The new tables for such construction are consistent with the goals of process and quality control provides signals that are consistent with each other and are easy to use.