scholarly journals A variable sampling interval EWMA t chart with auxiliary information – A robustness study in the presence of estimation error

2021 ◽  
Author(s):  
Peh Sang Ng ◽  
Michael B.C. Khoo ◽  
Sajal Saha ◽  
Ming Ha Lee
Keyword(s):  
Estimation Error ◽  
Auxiliary Information ◽  
Sampling Interval ◽  
Variable Sampling Interval ◽  
Variable Sampling

A combined variable sampling interval and double sampling control chart with auxiliary information for the process mean

2019 ◽  
Vol 42 (6) ◽  
pp. 1151-1165 ◽  
Author(s):  
Adamu A Umar ◽  
Michael BC Khoo ◽  
Sajal Saha ◽  
Abdul Haq
Keyword(s):  
Steady State ◽  
Control Charts ◽  
Auxiliary Information ◽  
Sampling Interval ◽  
Double Sampling ◽  
Process Mean ◽  
Small Shift ◽  
Average Time To Signal ◽  
Variable Sampling Interval ◽  
Variable Sampling

In recent years, the suitable use of auxiliary information technique in control charts has shown an improved run length performance compared to control charts that do not have this feature. This article proposes a combined variable sampling interval (VSI) and double sampling (DS) chart using the auxiliary information (AI) technique (called VSIDS-AI chart, hereafter). The plotting-statistic of the VSIDS-AI chart requires information from both the study and auxiliary variables to efficiently detect process mean shifts. The charting statistics, optimal design and performance assessment of the VSIDS-AI chart are discussed. The steady-state average time to signal (ssATS) and steady-state expected average time to signal (ssEATS) are considered as the performance measures. The ssATS and ssEATS results of the VSIDS-AI chart are compared with those of the DS AI, variable sample size and sampling interval AI, exponentially weighted moving average AI (EWMA-AI) and run sum AI (RS-AI) charts. The results of comparison show that the VSIDS-AI chart outperforms the charts under comparison for all shift sizes, except the EWMA-AI and RS-AI charts for small shift sizes. An illustrative example is provided to demonstrate the implementation of the VSIDS-AI chart.

The variable sampling interval X̄ chart with estimated parameters

2011 ◽  
Vol 28 (1) ◽  
pp. 19-34 ◽  
Author(s):  
Ying Zhang ◽  
Philippe Castagliola ◽  
Zhang Wu ◽  
Michael B. C. Khoo
Keyword(s):  
Sampling Interval ◽  
Variable Sampling Interval ◽  
Estimated Parameters ◽  
Variable Sampling
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