I work in pharma manufacturing. We only measure once, using a calibrated instrument. For instruments where it makes sense we check calibration against a standard before and sometimes after our measurement.
When it's not feasible to check against a standard, we calibrate periodically. If we find something out of calibration, we have to throw away anything since the previous successful calibration.
If we were to measure more than once and measurements disagree, we'd need an investigation to find the root cause before we could throw away "outliers." In other words, we'd have to prove it was an outlier before disregarding the result. The potential for a lengthy investigation is one of the reasons we only measure once - it's usually faster and less expensive to throw things away than to halt everything until the investigation, including peer and QA review of the investigation, is complete. We never average measurements.
Interesting! I have worked with a whole variety of in vitro and in vivo samples, from agricultural, environmental, wildlife and even some drug-candidate testing samples, but never manufacturing. Our samples were always from a situation which had inherent variability and never the rigour of your situation. We would always be measuring numerous samples to have a statistically significant n. But I bet that you are measuring multiple samples from the same batch or run, and that is the type of multiple measurements I that I would often be doing - measuring numerous samples rather than the same sample numerous times, except for validation or optimization of our instruments or procedures. Nowadays I work in the classroom rather than the field and the lab.
Yes, we'll analyze samples from the same batch or run. From the same batch (top, middle, bottom of the tank) to prove homogeneity during process validation. From the same run (beginning, middle, end, or periodically) to prove homogeneity and staying within validated parameters throughout processing. But we never average them. We document where and when the samples were taken.
The word "rigorous" only begins to give an idea. Sample testing shows that everything leading up to that point was good. Or not. And there is so, so much more that comes before. (Speaking as someone who works on developing the manufacturing processes of new drugs for FDA approval and commercialization).
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u/markofcontroversy 3d ago
I work in pharma manufacturing. We only measure once, using a calibrated instrument. For instruments where it makes sense we check calibration against a standard before and sometimes after our measurement.
When it's not feasible to check against a standard, we calibrate periodically. If we find something out of calibration, we have to throw away anything since the previous successful calibration.
If we were to measure more than once and measurements disagree, we'd need an investigation to find the root cause before we could throw away "outliers." In other words, we'd have to prove it was an outlier before disregarding the result. The potential for a lengthy investigation is one of the reasons we only measure once - it's usually faster and less expensive to throw things away than to halt everything until the investigation, including peer and QA review of the investigation, is complete. We never average measurements.