Behnken, Donald W. (1957, ASQC) E. I. DuPont de Nemours & Company
The moving trend control chart is discussed as a means of controlling laboratory materials tests where the measured property of the standard changes gradually (usually a decline) with respect to the time. Methods are discussed for calculating the central line and control limits for linear trends. A tabulation method is presented for determining control limits for processes whose trends are non-linear.
Statistical process control (SPC)