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Proper subgroup size for statistical process control
Author(s) -
Holmes Donald S.,
Mergen A. Erhan
Publication year - 1988
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.4680040408
Subject(s) - statistical process control , statistics , process (computing) , control chart , statistical hypothesis testing , variance (accounting) , mathematics , process control , subgroup analysis , computer science , reliability engineering , engineering , accounting , confidence interval , business , operating system
This paper deals with an approach for choosing the proper subgroup size for control charts. The approach is particularly appropriate for batch industries where some batch‐to‐batch variation is to be expected and should be accommodated. It uses two tests to evaluate the proper subgroup sizes. The tests are ANOVA for testing that the process mean is in control and Bartlett's test for testing that the process variance is in control. Besides the two tests the width of the process from measurements based on the selected subgroup size needs to be compared with the desired specification limits. An example is included to illustrate the use of the approach.