Setting process control chart limits for rounded-off measurements

Measurements can often be imprecise and subjected to rounding-off. Typically, this rounding-off is ignored and assumed to have little to no effect. However, when the measuring scale step is not negligible, it may affect statistical control tools such as X‾-chart. Designing statistical process contro...

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Bibliographic Details
Published in:Heliyon 2023-03, Vol.9 (3), p.e13655-e13655, Article e13655
Main Authors: Etgar, Ran, Freund, Sarit
Format: Article
Language:English
Subjects:
Measurement
Quality control
Round-off
Rounding error
Statistical process control
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Summary:Measurements can often be imprecise and subjected to rounding-off. Typically, this rounding-off is ignored and assumed to have little to no effect. However, when the measuring scale step is not negligible, it may affect statistical control tools such as X‾-chart. Designing statistical process controls without considering the effects of rounding leads to high exposure to false negative results. This study illustrates the effects of rounding on the X-chart and shows that the result may further deteriorate due to asymmetry (incompatibility of the process and the measuring device parameters). A new simple method to design control limits is proposed, based on maintaining the original characteristics of the chart as devised by Shewhart.
ISSN:2405-8440
2405-8440
DOI:10.1016/j.heliyon.2023.e13655