A variable sample size run sum coefficient of variation chart
Document Type
Article
Publication Date
6-1-2022
Abstract
A run sum chart with variable sample size (VSS) to detect shifts in the coefficient of variation (gamma) is proposed. The run sum gamma chart divides the chart into different regions with distinct scores assigned to these regions, and evaluates the process from the cumulative score. The proposed chart varies the sample size based on the cumulative score. A detailed description of the operation for the proposed chart is provided. Formulae to evaluate various performance measures are also derived. Furthermore, algorithms to optimize the chart are proposed. The chart significantly outperforms the run sum gamma chart without the VSS feature in most cases. Besides the run sum gamma chart, comparisons are also made against other gamma charts. Finally, the implementation of the VSS run sum gamma chart is shown on an illustrative example.
Keywords
Average run length, Coefficient of variation, Expected average run length, Run sum, Variable sample size
Divisions
MathematicalSciences
Funders
Fundamental Research Grant Scheme (Grant No: FP052-2018A),Research University Grant (Grant No: GPF030B-2018)
Publication Title
Quality and Reliability Engineering International
Volume
38
Issue
4
Publisher
Wiley
Publisher Location
111 RIVER ST, HOBOKEN 07030-5774, NJ USA