The Reliability of Assigned Values from the GeoPT Proficiency Testing Programme from an Evaluation of Data for Six Test Materials that have been Characterised as Certified Reference Materials.

Assigned values derived from the GeoPT proficiency testing programme were compared with certified values for six certified reference materials that have been used as test materials in the GeoPT programme. Statistical analysis showed that there were few significant differences between these sets of data and that these differences had no significant impact on the GeoPT assessment when fitness-for-purpose criteria were taken into account. [ABSTRACT FROM AUTHOR]