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

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

Histograms

Bias (Deviation from Mean)

Z-Scores

TPI (Industry)

PTP and Site Precision Comparisons

5.2.2 Tools and Approaches for Responsible Standards Development Groups.

TPI and precision trends

Bias via box & whisker plots

Normality evaluations

Relative standard deviations

Uncontrolled variables

Reference is made in this guide to the ASTM International Interlaboratory Cross-Check Program (ILCP) on Petroleum Products and Lubricants. 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.