DynaCal – Decision Rules for Stating Conformity

Introduction

Calibration certificates serve as crucial documents in the field of metrology, providing traceable evidence of the accuracy and reliability of measurements. A central responsibility of calibration laboratories such as DynaCal, LLC. DynaCal is to communicate whether a measurement result complies with specified requirements. This process, known as stating conformity, must consider both the measured value and the associated measurement uncertainty to ensure that the declaration is technically sound and meaningful. This policy outlines DynaCal’s approach to making statements of conformity, the decision rules employed, and the communication protocol for customers.

Technical Basis and Philosophy

At the heart of this policy is the understanding that any declaration of conformity—such as “pass/fail” or “in-tolerance/out-of-tolerance”—must reflect not only the measured value but the combined effects of measurement bias and uncertainty. Conformity is determined by assessing whether the true value of the measured quantity is expected to lie within a specified range, defined by the applicable specification or standard, and at a specified level of statistical confidence.

The technical justification for this approach rests on two pillars:

• Inclusion of Measurement Uncertainty: Any statement of conformity must take into account the total measurement uncertainty, which includes the effects of known biases and random variation.
• Statistical Confidence: The range of values within which the true value is expected to lie is determined with an associated confidence level, typically based on the coverage factor used in uncertainty analysis.

Customer Requests and Communication

When a customer requests a statement of conformity to a specification or standard for a test or calibration, it is essential for DYNACAL to ensure that both the specification/standard and the decision rule are clearly defined and mutually understood. The customer must be made aware of, and agree with, the decision rule, unless that rule is inherently specified by the referenced standard or document.

To facilitate clear communication and avoid misunderstandings, DYNACAL follows these steps:

• Clear Definition of Requirements: DYNACAL works with the customer to ensure specifications and standards are explicitly stated on purchase orders or other communication channels.
• Decision Rule Disclosure: Unless inherently defined by the standard, the decision rule to be used for conformity statements will be discussed and agreed upon before testing or calibration commences.
• Customer-Driven Rules: If the customer, regulatory authority, or normative document prescribes a decision rule, DYNACAL will follow it without further consideration of associated risks, as long as it is feasible within the laboratory’s capabilities.

Application of Decision Rules

The decision rule is the protocol used to determine whether a measured result meets a specified requirement, given the measurement uncertainty. DynaCal’s policy is guided by a commitment to transparency, technical competence, and risk mitigation for false accept (Type I error) and false reject (Type II error) outcomes.

When making statements of conformity, DYNACAL:

• Documents the specific decision rule employed (unless it is inherently part of the specification or standard).
• Takes into account the level of risk associated with the decision rule, including the probabilities of false accept and false reject, and any relevant statistical assumptions.
• Communicates explicitly which results the statement of conformity applies to, and which specifications, standards, or portions thereof are met or not met.

Scope and Applicability of the Policy

This policy specifically applies to calibration events where the resultant measurement error—the difference between the measured quantity value and the reference value—is evaluated against a product specification. In many cases, only the measurement result and its associated uncertainty are reported, in which case this policy is not applicable. The policy is relevant only when a formal statement of conformity to a defined requirement is requested.

Methodologies for Stating Conformity

DYNACAL bases its statements of conformity on two core methodologies:

• 4:1 Test Uncertainty Ratio: Where possible, DYNACAL maintains a Test Uncertainty Ratio (TUR) of no less than 4:1. This means that the width of the tolerance interval is at least four times greater than the expanded uncertainty of the measurement, ensuring high confidence that the result truly conforms to the specification.
• Guardbanding: In instances where a 4:1 TUR cannot be achieved, DYNACAL employs a guardbanding method. Guardbanding reduces the risk of false acceptance by narrowing the acceptance zone, thus increasing confidence that products declared as compliant are indeed conforming, even when uncertainty is relatively large compared to the tolerance.

Both approaches mitigate the risks associated with measurement uncertainty in conformity assessment, and the choice between them depends on the technical feasibility within each calibration scenario.

Customer Options and Exceptions

If a customer does not accept the default methodologies outlined above (4:1 TUR and/or guardbanding as appropriate), this must be made clear to DYNACAL at the time of the service request. Customers are encouraged to specify any preferred decision rules on their purchase orders or directly with DynaCal’s customer service team. While DYNACAL strives to accommodate all reasonable requests, the laboratory reserves the right to decline requests for alternative decision rules that are technically unfeasible or incompatible with laboratory constraints.

Documentation and Record Keeping

For every calibration event where a statement of conformity is provided, DYNACAL documents:

• The decision rule employed, including any statistical assumptions.
• The measurement result and associated uncertainty.
• Which requirements were evaluated, and whether those requirements were met.
• Any communication with the customer regarding the specification of the decision rule.

This documentation ensures traceability, transparency, and compliance with accreditation requirements.

Conclusion

DynaCal’s policy for making statements of conformity in calibration certificates is built on principles of transparency, technical rigor, and risk mitigation. By clearly defining requirements, communicating decision rules, and rigorously accounting for measurement uncertainty, DYNACAL ensures that its conformity statements are both meaningful and defensible. Customers are encouraged to engage with DYNACAL at the outset of any calibration project to ensure that the approach used aligns with their technical and regulatory needs.

This comprehensive policy offers confidence to customers, regulators, and end-users that DynaCal’s statements of conformity are reliable, traceable, and firmly grounded in international best practices for calibration and measurement science.

DynaCal, LLC

Dated August 2, 2025