“…For more details, readers may refer to Isaki, [12] Naik and Gupta, [13] Upadhyaya and Singh, [14] Magnus, [15] Singh et al, [16] Shu et al, [17] Riaz, [18,19] Cheng and Chen, [20] Sodipo, [21] Riaz, [22] Yadav, [23] Singh and Solanki, [24] Grover and Kaur. [25] Riaz [18] proposed the Vr control chart for monitoring process variability using the information of an auxiliary variable based on a regression-type estimator of variance and showed that its performance increases as the correlation between the main variable and the auxiliary variable increases. Riaz [19] proposed a control chart to monitor process variability using the auxiliary information.…”