This is an editorial resource on representative sampling: how a small quantity is taken from a much larger quantity so that a figure measured on the small one can honestly be written about the large one, what a sampling plan has to fix before anybody lifts a scoop, and the specific ways a result stops describing the thing it was supposed to describe.
Almost every figure anyone quotes about a large quantity was measured on a very small part of it. A number on a certificate may have been produced from a few milligrams out of many grams, and everything that happened between the large quantity and those few milligrams is invisible by the time the figure is printed. That step is usually the largest single source of error in the whole exercise, and it is the only one that no amount of care in the instrument room can undo.
Sampling fails quietly, and it fails in ways that look like good practice: taking from the top because the top is reachable, taking one increment instead of several because the material “looks the same all through”, splitting a sample by pouring off half, labelling at the end of the round rather than at the moment. Each is defensible on the day. Together they produce a figure that is precise, reproducible and about something other than the batch.
The guide on the front page is written for small settings, where one or two people do everything and there is no quality department to fall back on. The standards it draws on were written for large regulated operations, but the reasoning is not regulatory. It is arithmetic about what a part can be made to say about a whole.
The guide is written to be read once and used afterwards. It states what a given sampling scheme can establish and, in the same breath, what it cannot. Where a practice has a cheaper proportionate version for a small setting, the guide says so rather than pretending that every reader has a sampling department and a spinning riffler.
It is deliberately general. It does not describe, recommend, compare or make any claim about any material, item, treatment or substance, and it never tells a reader what to do with one.
If something here is wrong, we would rather know. Write to editor@mypeptsuk.com with the passage and what it should say. Substantive corrections are made on the page itself and the review date at the top of this page is updated.
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