ISO/TR 7242:1981 PDF

Name: ISO/TR 7242:1981 — Chemical analysis of light metals and their alloys — Statistical interpretation of inter-laboratory trials
SKU: ISO/TR 7242:1981
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Chemical analysis of light metals and their alloys — Statistical interpretation of inter-laboratory trials

Название (английский):

ISO/TR 7242:1981

Chemical analysis of light metals and their alloys — Statistical interpretation of inter-laboratory trials

Статус документа:: Действующий
Формат:: Электронный (PDF)
Количество страниц:: 15
Дата публикации:: 1 июня 1981 г.
Издание:: ISO TR 7242 edition 1 version 1
ICS:: 77.120.01

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Описание (английский):

This Technical Report constitutes an attempt to explain the numerical results of a statistical examination in the simplest possible way and to show how statistical results can be used in laboratory practice. This simplified method is applicable when the number of laboratories is not more than 20 and when the number of results per laboratory is not more than 10.

Abstract

Похожие стандарты

Другие стандарты ISO

Overview

ISO/TR 7242:1981 is an ISO Technical Report that provides practical guidance for the statistical interpretation of inter‑laboratory trials in the chemical analysis of light metals and their alloys. It is informative (not normative) and aimed at helping analysts and laboratories understand and use statistical results from round‑robin and comparative analytical trials. The report emphasizes a simplified method suitable when the number of participating laboratories does not exceed 20 and the number of results per laboratory does not exceed 10.

Key topics

Scope and purpose: Explains numerical results of statistical examinations and how they can be applied in laboratory practice for light metals.

Basic symbols and statistics: Defines arithmetic mean, estimated standard deviations (within‑laboratory SW, between‑laboratory Sb, total St), and relative standard deviation (coefficient of variation).

Repeatability and reproducibility: Shows how to separate experimental dispersion (repeatability) from laboratory/method effects (reproducibility).

Laboratory effect testing: Uses dispersion‑ratio tests (Snedecor / F‑type reasoning) and provides simplified range‑based procedures to determine whether observed differences between laboratory means are significant.

Rapid, range‑based method: A practical procedure using ranges and lookup tables (annex tables) for:

detecting aberrant laboratories (Dixon test),
checking homogeneity of internal dispersions,
estimating common experimental dispersion from mean ranges,
testing for a laboratory effect and estimating Sb when present.

Confidence intervals: Guidance for computing confidence intervals for single determinations or for means, using Student’s t and pooled standard deviations; formulas relate SR (standard deviation of reproducibility) to SW and Sb and how SR varies with the number of replicates n.

Worked example: Interpretation illustrated by chromium determination data (methods A and B) to demonstrate calculation and interpretation.

Applications

ISO/TR 7242:1981 is useful for:

Analytical chemists and metallurgical laboratories conducting inter‑laboratory (round‑robin) trials for light metals and alloys.

Quality‑assurance teams validating analytical methods or comparing laboratory performance.

Standardization bodies and technical committees seeking objective, practical interpretation of comparative trial data.

Statisticians supporting laboratory networks who require a simplified, table‑based approach when participant counts are modest (≤20 labs, ≤10 replicates).

Related information

Produced by ISO/TC 79 (Light metals and their alloys), this Technical Report complements standard statistical references (Student’s t, Snedecor F) and standardized calculation practices for inter‑laboratory studies. It provides practical, non‑normative guidance rather than prescriptive requirements.

Keywords: ISO TR 7242, inter‑laboratory trials, statistical interpretation, light metals, repeatability, reproducibility, round‑robin, confidence interval, Dixon test.

ISO/TR 7242:1981 PDF

Abstract

Похожие стандарты

Overview

Key topics

Applications

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