Does a test report pass near the limit count?
A pass near the acceptance limit needs the laboratory's explanation of how it reached that decision. Ask for the measurement uncertainty and the decision rule before using the result to approve shipment. Cambridge China Bridge can help buyers put these questions to the laboratory and factory.
Start with the decision rule
UKAS describes a decision rule as the agreed process for making a conformity decision. When a result sits close to the limit, ask the laboratory to explain the rule applied to that result, rather than relying on the word pass.
Check the report's identity separately using product test report verification. An authentic report still needs a clear explanation of a borderline decision.
Ask what the uncertainty means
Measurement uncertainty describes the doubt associated with a measured value. It is different from the product's permitted tolerance. Ask for the uncertainty applicable to the particular result, its units and the meaning of any accompanying confidence statement.
Ask whether the uncertainty interval extends across the specification limit and how the laboratory treated that situation. Do not add or subtract uncertainty yourself to turn an uncomfortable result into a preferred outcome.
Send the laboratory a specific question
Write: “Please explain the decision rule used for this result, how measurement uncertainty was taken into account, and why the reported outcome is pass. Please identify the specification limit and the acceptance boundary used.”
Also ask whether a guard band was used, meaning a margin between the specification limit and the acceptance boundary. If the laboratory says uncertainty was already addressed by the test method, ask it to identify the relevant wording and explain how it applies here.
Resolve the result before releasing goods
Keep shipment approval pending while the explanation is unresolved. Ask the laboratory whether a corrected report, further measurement or a different sample is appropriate. Agree the purpose and interpretation of any repeat test before commissioning it; retain the original result.
Check that the tested sample represents the material, finish and construction being shipped. Use checking whether a report covers your order for that separate question. A borderline result is a reason to examine production consistency, not just the report wording.
Working out your own order? Send us the product on WhatsApp and we reply the same working day: WhatsApp us
Make the next testing brief clearer
Before testing, ask the laboratory to confirm the specification, decision rule, treatment of uncertainty and possible outcomes in writing. Ask how it will report a result that cannot support a clear decision under that rule.
Keep the explanation with the report, sample identity and your release decision. Use building a product compliance file to organise the wider records. Cambridge China Bridge's staff in China can help connect laboratory questions with factory sample and production records.
Frequently asked questions
Does a pass close to the limit mean I can ship?
Ask the laboratory to explain the decision rule and uncertainty first. Keep shipment approval pending if that explanation or the connection between the sample and your goods remains unresolved.
Does uncertainty crossing the limit mean a fail?
Do not decide from the interval alone. Ask the laboratory how its decision rule treats that result and why the reported conclusion follows.
Can I subtract uncertainty to get a pass?
Do not adjust the result yourself. Ask the laboratory to show how uncertainty was handled under the rule used for the report.
Should I retest a borderline pass?
Ask what a repeat test would resolve, which sample should be used and how the outcome would be interpreted. Keep the original report and the explanation alongside any repeat result.