Abstract:

In this article we extend quality control research into nominal and ordinal data from simple monitors of location to those of variability. Given ordinal data more traditional process control relies on demerit systems that explicitly monitor central location but not the distribution spread. It is quantified here in terms borrowed from ecology. An established index of diversity and its standard error are the basis for a new quality control chart that we have also assessed with respect to error rates.
Received on November 19 2010; revised on March 15 and April 6, 2011
References: 09