Exponentially Weighted Moving Average (EWMA) Chart Based on Six Delta Initiatives

Abstract

A control chart is a graphical device for representation of the data for knowing the extent of variations from the expected standard. The technique of control chart was suggested by W.A. Shewhart of Bell Telephone Company based on three sigma limits. M. Harry, the engineer of Motorola has introduced the concept of six sigma in 1980. In six sigma initiatives, it is expected to produce 3.4 or less number of defects per million of opportunities. Moderate distribution proposed by Naik and Desai is a sound alternative of normal distribution, which has mean and mean deviation as pivotal parameters and which has properties similar to normal distribution. Naik and Tailor have developed various control charts based on this distribution. In this paper an attempt is made to construct a control chart based on six delta initiatives for exponentially weighted moving average chart. Suitable Table for mean deviation is also constructed and presented for the engineers for making quick decisions.