Economic Design of X̅ Control Chart under Double EWMA

Designing of parameters plays an important role in economic design of control charts for lowering the cost and time. Manipulating sample size (n) and sampling interval (h), the effect of double exponentially weighted moving average (DEWMA) model was studied for the Economic Design (ED) of X̅ control chart. Optimum sizes and level were obtained when the characteristics of an item possesses DEWMA model. When shifts are uncertain the optimal design for DEWMA chart should be more conservative and should be implemented for benefiting the consumers as well as producers

Economic Design of X Control Chart for DEWMA under Non-Normal Population

In this paper, mathematical investigation has been made to study the effect of double exponentially weighted moving average (DEWMA) model on economic design of X control chart for non-normal population. Formulae are derived for calculating the value of n and h when the characteristics of an item posses DEWMA model. The sample mean of DEWMA model has been represented by first four terms of an Edgeworth series. A numerical example is given to verify the performance of DEWMA model in the presence of non-normality. The DEWMA charts working together with non-normality affects the control chart scheme when small to moderate shifts in the mean of the controlled parameter are expected. It is found that when shifts are uncertain the optimal design for DEWMA chart should be more conservative