A Statistical Control Chart for Process with Correlated Subgroups

Abstract

In this paper a new control chart which accounts for correlation between process subgroups will be proposed. We consider the case where the process fluctuations are autocorrelated by a stationary AR(1) time series and where n($\geq1$) items are sampled from the process at each sampling time. A simulation study is presented and shows that for correlated subgroups, the proposed control chart makes a significant improvement over the traditionally employed X-bar chart which ignores subgroup correlations. Finally, we illustrate the proposed chart by comparing the standardized residuals and X-bar chart on a data set of motor shaft diameters.

Keywords

File

Download PDF

References

1. Communications in Statistics, Theory and Methods v.21 Effects of autocorrelation on control chart performance Alwan, L.C.
2. Introduction to Time Series and Forecasting Brockwell, P.J.;Davis, R.A.
3. Statistical Quality Design and Control Dever, R.E.;Chang, T.H.;Sutherland, J.W.
4. Canadian Journal of Chemical Engineering v.69 Statistical process control procedure for correlated observation Harris, T.J.;Ross, W.H.
5. Simulation and Computation v.21 On the α-risks for Shewhart control charts Padgett, C.S.;Thombs, L.A.;Padgett, W.J.
6. Technometrics v.32 Control charts for detecting cyclical behavior Spurrier, J.D.;Thombs, L.A.
7. Communications in Statistics, Simulation and Computation v.23 An evaluation of forecast-based quality control schemes Superville, C.R.;Adams, B.M.
8. Technometrics v.38 Control Charts for Detection of a Periodic Component Tatum, L.G.
9. Journal of Quality Technology v.10 Modification of control chart limits in the presence of data correlation Wardell, D.G.;Moskowitz,H.;Plante, R.D.
10. Technometrics v.35 Performance of CUSUM control schemes for serially correlated observations Yaschin, E.
11. Technometrics v.40 A statistical Control Chart for Stationary Process Data Zhang, N.F.