Robust Location Estimators for the Ū Control Chart

Marit Schoonhoven, Hafiz Z. Nazir, Muhammad Riaz, Ronald J. M. M. Does
2011 Journal of QualityTechnology  
This article studies estimation methods for the location parameter. We consider several robust location estimators as well as several estimation methods based on a phase I analysis, i.e., the use of a control chart to study a historical dataset retrospectively to identify disturbances. In addition, we propose a new type of phase I analysis. The estimation methods are evaluated in terms of their mean-squared errors and their e↵ect on the X control charts used for real-time process monitoring
more » ... cess monitoring (phase II). It turns out that the phase I control chart based on the trimmed trimean far outperforms the existing estimation methods. This method has therefore proven to be very suitable for determining X phase II control chart limits. In this article, we compare existing and new methods for estimating the in-control µ. The collection of TM i = (Q i,1 + 2Q i,2 + Q i,3 )/4, where Q i,q is the qth quartile of sample i, q = 1, 2, 3 (cf.
doi:10.1080/00224065.2011.11917870 fatcat:7bnzmziosffkrn2nd22wjw6fqq