Evaluation of the quality of measurements of the testing laboratory during interlaboratory comparative tests

Abstract

The article presents the statistical processing of the test results of the mass fraction of the chlorine ion (Cl) obtained from two accredited testing laboratories. The stages of statistical processing of the results of interlaboratory comparison tests are as follows: elimination of gross errors, determination of the uniformity of the sample, calculation of the assigned value, evaluation of the quality of the measurement results. The presence of gross errors in the sample was determined by the Grubbs test, and the uniformity of the sample was confirmed by the Fisher’s test and Student’s test. The assigned value was calculated by a robust method using algorithm A with an iterative scale. The quality of laboratory measurement results was evaluated using the z-score. The z-score value for each participant showed that the results of measuring the mass fraction of chlorine ion in cement samples were acceptable. The quality of the results of these laboratories is satisfactory and does not require corrective measures. These results of the test quality assessment can be used for the organizers of interlaboratory tests, as well as for accredited laboratories that check their qualifications.

Keywords

• interlaboratory comparison
• proficiency testing
• robust method
• assigned value
• measurement error
• outlier
• standard deviation for proficiency assessment