np-Charts for attribute control

Leiva, Victor; Oliveira, Amilcar

http://hdl.handle.net/10400.2/10715

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Authors

Leiva, Victor

Oliveira, Amilcar

Abstract(s)

In this article, we introduce charts for attribute control considering the number of defective items, named np‐charts. These charts are preferable over charts for proportion (p) of defective items, named p‐charts, when the sample size (n) remains constant for all subgroups. The benefits of using np‐charts over p‐charts are: an easier interpretation and the fact that no calculation is required for each sample result. We provide a review of the basic issues related to np‐charts and some recent ideas on the topic based on life distributions. In addition, we discuss an implementation of np‐charts in the R software by using examples with data on attributes and lifetimes.