Reconciling a supplier certificate with an independent result

Reconciling a supplier certificate with an independent result — setting out what I have, and where I think it stops being reliable.

Reconciling a supplier certificate: setting out the arithmetic in full, because I have had to do it twice and I would rather nobody else did.

Every step is shown. If the answer is wrong the error will be visible, which is the point of writing it out rather than posting the result.

Comparing your result to somebody else's on a different lot is not a comparison of suppliers. Lot is the unit and it should be in every report.

The opening post describes the usual case. This is about the unusual one.

Include the sample handling: how it was stored, how it travelled to the laboratory, how long it sat. A result on badly handled material is measuring the handling.

Happy to expand any of that if it is the useful part.

Adding the measurement that post #3 says would settle it.

Temporal patterns: if results from a supplier were good two years ago but have deteriorated recently, that is information. If they have been consistent over years, that is also information.

Worth checking against a second source before it gets quoted onward.

Photograph the vial and the label before opening. It costs ten seconds and it is what turns a report into something checkable.

Building on post #3 rather than restating it.

Reports naming a supplier need the evidence attached, which is a guideline rather than a formality. It is what makes the record usable and it is what keeps it fair.

I would want a second opinion before relying on that.

Answering the question post #3 raises rather than the one it answers.

Report the certificate figure alongside the independent one. The comparison is the point and it is the part most often omitted.

Someone will know this better than I do and I hope they say so.

That is the distinction I keep failing to hold on to. Written down now.

Post #7 and I disagree about the size of the effect, not about the direction.

Blind submission is worth the effort: have someone else relabel the sample so neither you nor the laboratory knows which supplier it came from until the result is back. Blind results change minds; self-selected results do not.

I am describing what is, rather than arguing for what should be.

Taking post #7 at face value and following it one step further.

Where you have no independent result, a documentation report is still worth filing: what the certificate contained, what it omitted, and how fast a request was answered.

This is where my knowledge stops and I would rather mark the edge than blur it.

If the supplier was asked about a discrepancy, include what they said verbatim rather than summarised. The wording of a response is informative.

Post #10 describes the usual case. This is about the unusual one.

Structured report format: compound, lot, independent testing service, method as reported, result, and the certificate figure for the same lot. One lot is one lot. It becomes a pattern at three or four, and it becomes a disputed record when asked and not explained.

Confirming post #12 from a second method, which matters more than confirming it from a second person.

Date the report: when the analysis was done matters. Material can degrade in storage. A report from two years ago is still useful but is not evidence about the current state of the same supplier's stock.

The format we ask for is compound, lot, testing service, method as reported, result, and the certificate figure for the same lot. A report missing any of those goes to the discussion rather than the record.

I would put a moderate confidence on that and no more.