Overview
ISO/TR 24697:2011 - Textiles and textile products: Guidelines on the determination of the precision of a standard test method by interlaboratory trials is a Technical Report that provides guidance for evaluating the precision (repeatability and reproducibility) of textile test methods using interlaboratory trials. It is informative (not normative) and is intended for test methods that produce a single numerical result on a continuous scale (including results calculated from several measurements). The report assumes a unimodal, approximately normal distribution of results and excludes discrete, pass/fail, ranking or accept/reject type methods.
Key topics and technical requirements
- Scope limitation: Applies only to continuous-scale test methods yielding a single numeric result; non-Gaussian data require different approaches.
- Trial design: Guidance on the number of laboratories, levels (types of material), replicates and testing order. Minimum recommended participation is at least five laboratories from three countries and a total of ≥30 samples (preferably ~60); e.g., with five labs, at least six material levels.
- Roles and responsibilities:
- Project manager: organizes the trial, collates results, and oversees statistical analysis (may appoint a statistician).
- Laboratory contact: receives samples and instructions, supervises operators and reporting.
- Operators: competent personnel who perform tests per instructions.
- Sample handling and randomization: Prepare sufficient homogeneous samples, label with random numbers known only to the project manager, and include reserves for losses.
- Reporting and forms: Standardized reporting templates (Annex A) for raw data, averages and within-cell spread.
- Data treatment and analysis:
- Missing data can be ignored unless excessive.
- Outliers should not be rejected except for demonstrated error or clear statistical criteria (see ISO 5725-2).
- Check homogeneity of variance (e.g., Cochran’s test) before pooling; calculate repeatability and reproducibility (Annex B provides statistical assessment guidance).
Practical applications and users
Who benefits:
- Standards committees and test method developers drafting or validating textile test methods.
- Laboratory managers and quality assurance teams in textile manufacturing and testing labs.
- Statisticians conducting interlaboratory studies to establish precision statements for standards.
- Certification bodies and regulatory stakeholders relying on quantitative textile test results.
Why use it:
- To quantify and document measurement precision for a test method.
- To support robust method validation, quality control and international acceptance of test methods.
- To inform decision-making by reporting not only averages but the expected variability (standard error, repeatability, reproducibility).
Related standards
- ISO 5725-2 - Basic method for determination of repeatability and reproducibility.
- ISO 5725-6 - Use in practice of accuracy values.
- ISO 3534-1 - Statistics: vocabulary and symbols.
Keywords: ISO/TR 24697:2011, textile test precision, interlaboratory trials, repeatability, reproducibility, ISO 5725, statistical assessment, test method validation.