Control charts for the coefficient of variation

The coefficient of variation (CV) has received an extensive attention in quality control. The existing control charts for monitoring the two-sided changes in the CV do not consider the average run length (ARL) unbiased criterion. In practice, the practitioners prefer the ARL-unbiased control charts. This paper proposes an ARL-unbiased Shewhart-type control chart to monitor the two-sided shifts in the CV. Then an ARL-unbiased synthetic chart in which the conforming run length sub-chart only needs a lower control limit is proposed to improve the performance of the ARL-unbiased Shewhart-type chart. The comparison results show that the proposed synthetic chart outperforms the proposed ARL-unbiased control chart in terms of the ARL. The effects of the parameter estimation on the proposed charts are also studied. Finally, a real example is used to illustrate the proposed control charts.

[1]  George Tagaras,et al.  Economic X̄ Charts with Asymmetric Control Limits , 1989 .

[2]  Patrick D. Bourke,et al.  Detecting a shift in fraction nonconforming using runlength control charts with 100% inspection , 1991 .

[3]  Eui-Pyo Hong,et al.  Development of CV Control Chart Using EWMA Technique , 2008 .

[4]  George F. Reed,et al.  Use of Coefficient of Variation in Assessing Variability of Quantitative Assays , 2002, Clinical and Vaccine Immunology.

[5]  Philippe Castagliola,et al.  Some Recent Developments on the Effects of Parameter Estimation on Control Charts , 2014, Qual. Reliab. Eng. Int..

[6]  Giovanni Celano,et al.  Monitoring the Coefficient of Variation Using Control Charts with Run Rules , 2013 .

[7]  Charles W. Champ,et al.  Effects of Parameter Estimation on Control Chart Properties: A Literature Review , 2006 .

[8]  Maria E. Calzada,et al.  The Generalized Synthetic Chart , 2009 .

[9]  Giovanni Celano,et al.  Monitoring the Coefficient of Variation Using a Variable Sampling Interval Control Chart , 2013, Qual. Reliab. Eng. Int..

[10]  Richard L. Marcellus.  Operating characteristics of X-bar charts with asymmetric control limits , 2001 .

[11]  Maria E. Calzada,et al.  A synthetic control chart for the coefficient of variation , 2013 .

[12]  Changliang Zou,et al.  Nonparametric control chart based on change-point model , 2009 .

[13]  Peihua Qiu,et al.  Using p values to design statistical process control charts , 2013 .

[14]  E. S. Page.  CONTROL CHARTS WITH WARNING LINES , 1955 .

[15]  Giovanni Celano,et al.  Monitoring the Coefficient of Variation Using EWMA Charts , 2011 .

[16]  Bin Chen,et al.  A new exponentially weighted moving average control chart for monitoring the coefficient of variation , 2014, Comput. Ind. Eng..

[17]  Richard L. Marcellus.  Performance Measures for ―X Charts with Asymmetric Control Limits , 2006, Qual. Reliab. Eng. Int..

[18]  S. W. Roberts.  Control chart tests based on geometric moving averages , 2000 .

[19]  Douglas M. Hawkins,et al.  A Control Chart for the Coefficient of Variation , 2007 .

[20]  Berna Yazici,et al.  Asymmetric control limits for small samples , 2009 .

[21]  Huifen Chen,et al.  Comparisons of the symmetric and asymmetric control limits for X and R charts , 2010, Comput. Ind. Eng..

[22]  E. S. Page.  CONTINUOUS INSPECTION SCHEMES , 1954 .

[23]  Trevor A Spedding,et al.  A Synthetic Control Chart for Detecting Small Shifts in the Process Mean , 2000 .