This document specifies the process and methodology for the construction, operation, and maintenance of statistical control charts to assess if a laboratory's execution of a standard test method is in statistical control and how to establish and validate the 'in-statistical-control' status.
It specifies control charts that are most appropriate for ISO/TC 28 test methods where the dominant common cause variation is associated with the long term, multiple operator conditions. The control charts specified for determination of in-statistical-control are: Individual (I), Moving Range of 2 (MR2), and either the Exponentially Weighted Moving Average (EWMA) or zone-based run rules (similar to Western Electric (WE) run rules) as sensitivity enhancement strategy to support the I-chart.
The procedures in this document have been primarily designed for numerical results obtained from testing of control samples prepared from a homogenous source of petroleum and related products in a manner that preserves the homogeneity of properties of interest between control samples.
This document applies to properties of interest that are (known to be) stable over time, and for data sets with sufficient resolution to support validation of the assumption that the data distribution can be approximately represented by the Normal (Gaussian) model. Mitigating strategies are suggested for situations where the assumption cannot be validated.
Текущий статус : Under development
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Технический комитет:Petroleum and related products, fuels and lubricants from natural or synthetic sources