Journal of Quality Engineering and Management

Design of Risk-adjusted Bernoulli EWMA Control Chart with Estimated Parameters 

Document Type : Original Article

Authors

Razieh Ashrafi Nasrabadi 1
Amir Hossein Amiri 2

1 Master Student of Industrial Engineering, Department of Industrial Engineering, Faculty of Engineering, Shahed University, Tehran  

2 Associate Professor, Department of Industrial Engineering, Faculty of Engineering, Shahed University, Tehran

Abstract
 Typically, in order to evaluate the performance of control charts in the healthcare, the parameters of the control chart are assumed to be known; although usually in practice, these parameters are unknown, and the process parameters should be estimated in Phase I for process monitoring. When the estimated parameters are used instead of their known values, the performance of the control chart is affected. In this paper, first, a risk-adjusted Bernoulli EWMA control chart is proposed. Then, the effect of parameter estimation on in-control performance and out-of-control performance of the proposed control chart is examined. After that, the methods of increasing sample sizes as well as modifying the control limits are used to reduce this effect. The results of simulation studies are reported in terms of average run length, standard deviation of run length and coefficient of variation of run length criteria. The simulation results confirm the reduction of the effect of the parameters estimation by increasing the sample size and correcting the control limits. 

Keywords

Parameter Estimation
Exponentially Weighted Moving Average Control 
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Journal of Quality Engineering and Management
Volume 9, Issue 1
Spring 2019
Pages 1-10

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