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D4968-19 – Standard Test Method Technical Guide
📐 Scope and Key Terminology
ASTM D4968-19 is a standard practice meant to assist the subcommittees and sections of Committee D20 on Plastics with the process of standards evaluation during the mandatory five-year review established by ASTM. It is designed to complement the Form and Style for ASTM Standards (the “Blue Book”), not to replace it. This practice specifically addresses the formatting and data requirements for test methods and specifications under the jurisdiction of D20.
The standard clarifies critical terminology, drawing heavily from related ASTM practices. The definitions of precision conditions are fundamental to the review process.
| 🟦 Term | 📏 Definition Context | 📌 Reference Source |
|---|---|---|
| Repeatability | Precision under conditions where independent results are obtained on identical items in the same lab, by the same operator, using the same equipment, in short intervals. | E456 |
| Reproducibility | Precision under conditions where results are obtained on identical items in different labs, by different operators, using different equipment. | E456 |
| Mandatory Language | To be ICC code-compliant, standards must avoid the terms “may” and “should” except in definitions, appendixes, and non-mandatory notes. | D4968 Sec. 3.3 |
⏳ Annual Review and Revision Process
The core of D4968-19 is the tripartite flowchart system found in Annex A1. This system provides a structured path for revisers, ensuring consistency and completeness based on the state of the standard under review. The process is triggered either by the five-year review deadline or by a required technical change.
💡 Standard Practice Guidance: The process outlined in Fig. A1.1 and A1.2 ensures that every standard under the jurisdiction of Committee D20 is checked for editorial accuracy, technical relevance, and statistical validity during its lifecycle.
| 🟦 Review Flowchart | 🎯 Standard Status | ⚡ Primary Objective |
|---|---|---|
| Fig. A1.1 | Recently revised or reapproved | Streamlined review of technical and editorial accuracy. |
| Fig. A1.2 | Not revised or reapproved in 5+ years | Comprehensive review of data, relevance, and user needs. |
| Fig. A1.3 | Precision and Bias development | Outlines the interlaboratory study process (E691, E2653). |
📊 Statistical Foundations and Precision
D4968-19 integrates heavily with existing statistical standards. The mandatory review process demands a check on the “Precision and Bias” statement, which must be based on rigorous interlaboratory testing. The practice explicitly references Practice E691 for studies with six or more laboratories, and Practice E2653 for fire test methods when fewer than six laboratories are participating. Additionally, Practice E2935 is referenced for conducting equivalence testing in laboratory applications.
⚠️ Important Distinction: Note 1 of D4968-19 explicitly states that there is no known ISO equivalent to this standard. This makes the annual review process defined here unique to ASTM Committee D20 standards.
The practice is intended for use by Committee D20 when test methods and specifications are revised due to technical changes or upon their five-year review, ensuring all required elements from the “Blue Book” are present and the user interface is maximized for clarity.
❓ Frequently Asked Questions
🔍 How does D4968-19 interact with the ASTM “Blue Book”?
It is explicitly designed as a complement. While the Blue Book provides overarching form and style rules, D4968-19 provides a specific annual review workflow and checklist tailored to the needs of Committee D20 on Plastics.
💡 Which flowchart should I use for a standard that was just reapproved?
Use Figure A1.1, which outlines a review process for standards that have been revised or reapproved recently, focusing heavily on maintaining editorial and technical accuracy.
⚡ What are the core conditions required for a repeatability study?
Repeatability requires the same method, identical test items, the same laboratory, operator, and equipment, with tests conducted within short intervals of time (Terminology E456).
📌 Why does the practice specify stringent language rules regarding “may” and “should”?
Section 3.3 mandates avoidance of these terms in the mandatory body of the standard to comply with International Code Council (ICC) requirements, ensuring the text is explicitly directive and legally robust for code adoption.