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D1749-93 – Standard Test Method Technical Guide
🎯 Purpose and Scope of Interlaboratory Evaluation
According to the scope of ASTM D1749, the primary purpose of an interlaboratory study is to determine the variability in results caused by differences among laboratories when following a prescribed test method. The study also assesses the consistency of this variability across different materials and identifies the type of additional standardization needed, if any. A study may also be conducted to compare alternative test methods.
To achieve these objectives, a sound statistical design is essential. This practice is specifically written for the task group chairman responsible for preparing or revising a standard test method. It outlines the basic principles for planning the study, conducting the study (outlined in Section 11), and provides background information for understanding the analysis (Section 12) and interpretation (Sections 13-15) of the results.
⚠️ User Safety Responsibility: This standard does not purport to address all safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use (Section 1.6).
🧪 Planning the Study and Key Preliminary Steps
The standard emphasizes a structured approach, beginning with Formulating the Problem (Section 3). If the objective of the task group was not clearly defined upon its establishment, it must be determined through task group discussion and approval from the parent committee chairman.
Before launching a multi-laboratory study, a Preliminary Study Within One Laboratory is critical (Section 4). This phase requires the task group to investigate the several variables of the test method, both experimentally and theoretically. This includes surveying the literature and other sources for potential variability in the application of the method.
💡 Statistician Consultation: While a statistician is not absolutely necessary for the design, analysis, and interpretation of these studies, questions often arise that can be readily answered by a statistician familiar with the analysis used herein. The task group chairman should arrange to consult with a statistician whenever possible (Section 1.4).
📊 Key Referenced Standards and Methodology
A successful interlaboratory evaluation relies on a network of supporting documents. The table below summarizes the key referenced standards that provide the terminology, precision practice, and statistical methods required to fully implement D1749.
| 🟦 Standard | 📐 Title / Focus | 🎯 Role in Interlaboratory Evaluation |
|---|---|---|
| ASTM E 691 | Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method | Primary statistical framework for designing the study and analyzing results to determine precision. |
| ASTM E 178 | Practice for Dealing With Outlying Observations | Provides criteria for identifying and handling outlying test results that could distort the analysis. |
| TAPPI T 1200 | Interlaboratory evaluation of test methods to determine TAPPI repeatability and reproducibility | Directly similar to D1749; details the complete analysis using a set of typical data for the industry. |
| ASTM D 685 | Practice for Conditioning Paper and Paper Products for Testing | Ensures specimens are conditioned uniformly, controlling one of the key variables in the test method. |
The structured phases of the practice guide the user through the evaluation process from start to finish.
| ⚡ Phase | 📏 Section Reference | 📌 Key Activities |
|---|---|---|
| 🧠 Planning | Sections 1 – 10 | Formulating the problem; conducting a preliminary study; employing a sound statistical design. |
| ⚙️ Conducting | Section 11 | Executing the prescribed procedure for the interlaboratory study across participating labs. |
| 📊 Interpretation | Sections 12 – 15 | Analyzing data; estimating repeatability and reproducibility; interpreting the results. |
❓ Frequently Asked Questions
🔍 What is the main purpose of an interlaboratory evaluation per this standard?
The purpose is to determine the variability in results caused by differences among laboratories following a prescribed test method, the consistency of this variability from material to material, and the type of additional standardization needed. It is also used to estimate the precision of an existing method for publication.
💡 Who is the intended audience for ASTM D1749?
This practice is written for the task group chairman responsible for the preparation or the revision of a standard test method for paper and paper products. It tells him what information is needed to properly plan an interlaboratory study.
⚡ How does this standard relate to TAPPI T 1200?
ASTM D1749 is directly similar to TAPPI T 1200. While D1749 provides the basic principles for planning, conducting, and interpreting the study, TAPPI T 1200 details the specific statistical analysis using a set of typical data for the pulp and paper industry.
📌 Why is a preliminary laboratory study recommended?
A preliminary study within a single laboratory allows the task group to investigate the several variables of the test method (both experimentally and theoretically) before a costly multi-laboratory study is initiated. This includes a literature survey for possible sources of variability.