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Ian Mann is a metrology and laboratory-quality specialist credited with Brian Brookman as co-editor of the 2021 third edition of Selection, Use and Interpretation of Proficiency Testing (PT) Schemes by Brian Brookman and Ian Mann. The editorial page identifies him with SAS in Switzerland. This identifies the proficiency-testing author without attributing the careers of other people named Ian Mann to him.^[ref]

The guide connects proficiency testing with practical decisions about laboratory measurements. Its selection criteria ask whether a scheme's material, measurand, concentration range and assessment approach fit the laboratory's actual work. A comparison using an unsuitable material can fail to test the procedure for which competence is being assessed.^[ref]

An original example illustrates why interpretation needs the assessment criterion. For a participant result $x=102$, assigned value $x_{\mathrm{pt}}=100$ and standard deviation for proficiency assessment ${\sigma }_{\mathrm{pt}}=1$ in compatible units, the proficiency-test z-score isA scheme using ${\sigma }_{\mathrm{pt}}=2$ would give $z=1$ for the same result. The result and its difference from the reference did not improve; the assessment scale changed. The chosen standard deviation for proficiency assessment must therefore be read with the score.

A participant's reported standard uncertainty answers another question: how uncertain is that participant's measurement result? It is not automatically the scheme's performance criterion. The guide separates evaluation scores, assessment spread and laboratory investigation of unexpected results.^[ref] Mann's documented editorial contribution is to this shared measurement-quality guidance; no separate invention or personal experimental result is implied.

Edited by Brian Brookman and Ian Mann. Eurachem guide, third edition (2021), version EPT 2021:P3. Section 3 (printed p. 4) defines interlaboratory comparison and proficiency testing; §7.2.4 (pp. 16–17) gives performance scores, and §8.2.3 (p. 21) discusses selection of the assessment standard deviation.

Additional verified locators: §7.1 (printed p. 15) discusses robust treatment of participant results. §§7.2.2–7.2.3 (pp. 15–16) and Annex D.2–D.3 distinguish assigned-value methods and assessment-standard-deviation selection. §7.2.4 (pp. 16–18) defines z and modified z-prime scores and the common boundaries: absolute score at most 2 is satisfactory, between 2 and 3 is questionable, and at least 3 is unsatisfactory. §7.2.6 (p. 18) gives the assigned-value uncertainty criterion u(x_pt) less than 0.3 sigma_pt. Annex D.2 notes that formulation may not reproduce routine sample-preparation or recovery difficulties.

Additional item-specific locators: §3.4 (printed p. 4) defines a proficiency-test item to include a sample, product, artefact, reference material, equipment, standard, data set or other information used for proficiency testing. §8.2.3 (p. 21) requires item homogeneity and stability appropriate to a proposed stricter assessment scale. §8.3.3.4 (p. 24) identifies item deterioration, matrix differences and inadequate homogeneity or stability as possible scheme-related causes of discrepant results.