**6. Conclusions**

In this article, we evaluate the performance of the Shewhart control chart for location monitoring with estimated parameters. The study substantiates the effect of estimation error and the variability in the practitioners' choice of phase-I samples on the chart, especially when the samples are prone to outliers. Increasing the phase-I sample size (although not practicably) will to some extent reduce the gross impact on the Shewhart chart. The results of this study further prove that incorporation of the non-parametric outlier screening models, Tukey and MAD, in the design of the Shewhart chart is more practicable as it requires less phase-I samples and yields better results. Another advantage of this study lies in the simplicity of its design and ease of usage. The study rounds up with an illustrative example with a photolithography real data. A comparison of the two detection models, Tukey and MAD, reveals that duo relatively e fficient. The study is limited to operate within the univariate setup, while focusing on multivariate setup will be a grea<sup>t</sup> advantage and we plan a future study for that. Also, proposed charts are memory-less, which implies they are suitable for monitoring large shift. However, the idea of the study is not only applicable in Shewhart multivariate setup, but also extendable to other control charts, like exponentially weighted moving average and cumulative sum charts both univariate and multivariate setups.

**Author Contributions:** Conceptualization, I.A.R. and N.A.; Data curation, I.A.R. and M.R.A.; Investigation, M.H.L.; Methodology, N.A.; Resources, M.H.L.; Supervision, M.R. and M.R.A.; Writing—original draft, I.A.R.; Writing—review & editing, M.H.L., M.R. and N.A. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study was partially funded by the Ministry of Higher Education, Malaysia through the Industry-International Incentive Grant for Universiti Teknologi Malaysia (grant number 01M30).

**Conflicts of Interest:** The authors declare no conflict of interest.
