5.1 This guide can be used to evaluate the performance of a laboratory or group of laboratories participating in a proficiency test (PT) program involving petroleum and petroleum products.

5.2 Data accrued, using the techniques included in this guide, provide the ability to monitor analytical measurement system precision and bias. These data are useful for updating standard test methods, as well as for indicating areas of potential measurement system improvement for action by the laboratory. This guide serves both the individual participating laboratory and the responsible standards development group as follows:

5.2.1 Tools and Approaches for Participating Laboratories.

Administrative Reviews

Flagged Data and Investigations

Data Normality Checks

QQ Plots

Histograms

Bias (Deviation from Mean)

Z-Scores, Z′-Scores Trends

Precision Performance-TPI_IND, F-test

Comparison of PTP and Individual Laboratory Site Precision

5.2.2 Tools and Approaches for Responsible Standards Development Groups.

TPI and precision trends

Bias and precision comparisons via box & whisker plots

Normality evaluations

Relative standard deviations

Uncontrolled variables

5.3 Reference is made in this guide to the ASTM International Proficiency Test Program on Petroleum Products, Liquid Fuels, and Lubricants, version PTP 2.0 implemented in 2016-2017. Program reports containing similarly displayed results and statistical treatments may be available in other PT programs. Appendix X2 summarizes the statistical tools referenced in this guide and Appendix X3 is a collection of examples covering many of the approaches described in this guide.