Assignable Cause

A source of variation which is non-random;  a chang in the source("Vital few" variables) will produce a significant change of some nagnitued in the resonse(dependent variable), e.g., a correlation exists; the change nay be due to an intermitent in-phase effect or a constant cause system which may or may not be highly predictable; an assignable cause is often signaled by an excessive number of data points outside a control limit and/or a non-random pattern within the control linits; an unnatural source of variation; most often economical to eliminate.