The statistical performance of parametric control charts is questionable when the underlying process does not follow any specified probability distribution. Nonparametric control charts are the best substitute for this situation. On the other hand, the ranked set sampling technique is preferred over the simple random sampling technique because it reduces the variability of process parameters and improves the control chart’s performance. This study aims to offer a nonparametric double homogeneously weighted moving average control chart under Wilcoxon signed-rank test considering the ranked set sampling technique (regarded as NPDHWMA RSS ), to further enhance the process location monitoring. The proposed chart’s run-length performance is compared with competing control charts, such as DEWMA- X ¯ , NPDEWMA-SR, NPRDEWMA-SR, DHWMA, and NPHWMA RSS control charts. The comparison revealed that the proposed NPDHWMA RSS control chart outperformed the other competing control charts, particularly for small to moderate shifts in process location. Finally, a real-life application is also offered for quality practitioners to show the strength of the proposed control chart.

The recently introduced triple exponentially weighted moving average (TEWMA) chart is the extended form of the classical EWMA and double EWMA (DEWMA) charts. On the other hand, the auxiliary information-based (AIB) homogeneously weighted moving average ( HWMA AIB ) chart is used for the monitoring of process location shifts efficiently as compared to the HWMA chart. Combining TEWMA with HWMA features is a new idea and is not seen in the literature until now. So, the objective of this study is to combine the idea of HWMA AIB and TEWMA charts and propose an AIB triple HWMA, symbolized as THWMA AIB chart to further improve the process location shift monitoring. The proposed THWMA AIB chart is developed by combining the AIB double HWMA plotting statistic into the other HWMA chart. The numerical results are computed using the Monte Carlo simulation method. Average run length ( ARL ), relative ARL , performance comparison index, and extra quadratic loss are used as comparison tools for the proposed THWMA AIB chart with the classical EWMA, TEWMA, mixed HWMA-CUSUM (MHC), AIB EWMA ( EWMA AIB ), HWMA, double HWMA (DHWMA), HWMA AIB , AIB mixed EWMA-CUSUM ( MEC AIB ), and AIB mixed CUSUM-EWMA ( MCE AIB ) charts. Finally, a practical application is also provided for users to demonstrate the proposed study’s vitality.

The hybrid exponentially weighted moving average (HEWMA) control chart is an enhanced version of the EWMA control chart that monitors the process parameters effectively. Similarly, the auxiliary information-based (AIB) EWMA control charts are very efficient for monitoring process parameters. The purpose of this paper is to propose two new control charts for the improved monitoring of process dispersion referred to as HEWMA AIB 1 and HEWMA AIB 2 control charts. A simulation study is carried out to assess the performance of the proposed HEWMA AIB 1 and HEWMA AIB 2 control charts. Average run length, extra quadratic loss, relative average run length, and performance comparison index are used to compare the performance of the proposed control charts against the existing counterparts. The comparisons reveal the superiority of the proposed control charts against other competing control charts, particularly for small to moderate shifts in the process dispersion. Finally, a real-life data set from the glass industry is used to demonstrate the practical implementation of the proposed control charts.

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The study examined the export performance using a trend analysis approach. Export as a solid factor in development of any country, determining the trend of export performance is an economy which is important in analyzing the growth of the economy. A graphical demonstration showing the trend of export performance in Nigeria over time was displayed. It also identifies the major determinants of manufacture exports in Nigeria using ordinary least square approach which shows that an increase in the average tariff rate would lead to a decline in the manufacturing exports and it is statistically significant at the 5% level of significance. Capacity utilization has a negative and insignificant correlation with manufactured exports. Also, there is a positive and significant relationship between exchange rate and trade openness at 1 and 5% level of significance respectively.