A new approach to design efficient univariate control charts to monitor the process mean

Abstract

Designing of efficient control charts for monitoring manufacturing processes and identifying assignable cause of variations is of constant interest in statistical process control. The present study incorporates neoteric ranked set sampling to design more efficient Shewhart, cumulative sum, and exponentially weighted moving average control charts for monitoring the mean of normal process. Using Monte Carlo simulations, the performance of the proposed charts is evaluated and compared with competing control charts on the basis of average run length and standard deviation of the run length for detection of shift of a specific magnitude. The extra quadratic loss is used to assess the overall performance of the control charts to detect shifts of various magnitudes. To further support the findings, a simulation study is carried out which revealed the supremacy of the proposed control charts over the existing charts. A real data set from a combined cycle power plant is used to demonstrate the application of the proposed control charts.

A new nonparametric double exponentially weighted moving average control chart

“…δ max and δ min are the maximum and minimum values of the shifts considered in a process; for details, see Nawaz et al, 35 Reynolds and Stoumbos, 36 Wu et al, 37 and the references cited therein. δ max and δ min are the maximum and minimum values of the shifts considered in a process; for details, see Nawaz et al, 35 Reynolds and Stoumbos, 36 Wu et al, 37 and the references cited therein.…”

“…where ARL(δ) represents the ARL value of a control chart when the shift of size δ occurs in the process. δ max and δ min are the maximum and minimum values of the shifts considered in a process; for details, see Nawaz et al, 35 Reynolds and Stoumbos, 36 Wu et al, 37 and the references cited therein. A smaller value of EQL indicates the overall better performance of the chart.…”

A hybrid homogeneously weighted moving average control chart for process monitoring

“…In a bid to further increase the sensitivity of the control charts to small, moderate and large shifts, several design strategies and modifications of the control charts have been introduced by researchers, which have led to the development of new control charts. For some relevant papers on these new control charts, readers are referred to Capizzi and Masaroto, 4 Al‐Shabah, 5 Abbas et al 6 Graham et al 7 Abujiya et al 8 Abbas et al 9 Lu, 10 Sanusi et al 11 Aldosari et al 12 Haq, 13 Haq et al 14 Nawaz et al 15 and Adeoti and Malela‐Majika 16 . All of these control charts, as in the case of many papers, are based on the assumption that process parameters are known.…”

Efficient monitoring of coefficient of variation with an application to chemical reactor process

“…The NRSS is a more efficient sampling structure as compared to the SRS and RSS schemes. Recent control charting structures under NRSS scheme may be found in Nawaz et al, 53 Nawaz and Han, 54 Abbas et al, 55 Hussain et al, 56 and references therein. In the literature, the Shewhart CV chart is not designed under the NRSS scheme, in the best of our knowledge.…”