  In statistical process control, procedures are applied that require
relatively strict conditions for their use. If such assumptions are violated,
these methods become inefficient, leading to increased incidence of false
signals. Therefore, a robust version of control charts is sought to be less
sensitive with respect to a breach of normality and independence in
measurements. Robust control charts, however, usually increase the delay in the
detection of assignable causes. This negative effect can, to some extent, be
removed with the aid of an adaptive approach.
