QMS & EMS London

When Ellis Ott introduced the analysis of means (ANOM) technique in 1967, he used the average range as the basis for obtaining the ANOM detection limits. When Ed Schilling extended Ott’s technique in 1973, he also used the average range as the basis for obtaining the ANOM detection limits. In these early papers the scaling factors given were merely upper bounds on the exact values. In 1974 Lloyd Nelson recomputed these upper bounds to obtain more precise ANOM detection limits. However, in his work Nelson shifted from using the average range to using a different dispersion statistic. He used the root mean square within (RMSW). We will return to this in a moment.

In 1920, Sir Ronald A. Fisher invented a statistical way to compare data sets. Fisher called his method the analysis of variance, which was later dubbed an ANOVA. This method eventually evolved into Six Sigma data set comparisons.