Mitten, L. G.; Sanoh, A. (1961, ASQC) Northwestern University; Dai Nippon Spinning Co., Ltd., Japan
A number of devices have been proposed for increasing the efficiency of the X-Bar chart. Many of these violate one of the cardinal principles of practical statistical quality control--techniques must be simple if they are to be practical and useful. The X-Bar chart with warning limits is perhaps the most practical and popular of the modified X-Bar charts proposed to date.
Statistical process control (SPC)