On the question of special causes, Deming would say that they are
statistically determined. One can use an attribute chart to find the
mean, standard deviation, and control limits of the population's
performance. If the individuals concerned lie outside of the control
limits, you can eliminate them (one at a time, from the largest deviation
to the smallest). Recalculate to determine their effect on the
statistics.
Simple inferential statistics are a major part of Deming's system of
profound knowledge.
-- jzavacki@epix.net John Zavacki The Wolff Group 900 James Avenue Scranton, PA 18510 Phone: 717-346-1218 Fax: 717-346-1388