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On correct expression of variance of double progressive mean statistic for monitoring Poisson observations
Author(s) -
Abbas Zameer,
Nazir Hafiz Zafar,
Riaz Muhammad
Publication year - 2021
Publication title -
quality and reliability engineering international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.913
H-Index - 62
eISSN - 1099-1638
pISSN - 0748-8017
DOI - 10.1002/qre.2871
Subject(s) - statistic , variance (accounting) , poisson distribution , statistics , expression (computer science) , tracing , mathematics , computer science , econometrics , economics , accounting , programming language , operating system
Control charts play a vital role in tracing unfavorable changes in the ongoing process parameters to enhance the quality of the output. Attribute charting schemes are commonly utilized for tracing shifts in fraction nonconforming and number of nonconformities per unit in any production process. A double progressive mean charting structure for monitoring Poisson observations (PDPM) is recently proposed by Alevizakos and Koukouvinos 1 for efficient monitoring of the average number of nonconformities in the production unit. Unfortunately, the variance expression used in the charting statistic of the said article needs correction. The focus of this study is to provide correct derivation and expression of the variance of the PDPM statistic.