Philip Newton (pne) wrote,
Philip Newton

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Unwarranted precision

I was taking a multi-vitamin tablet this morning and looked at the packaging.

What I saw made me sad due to the unwarranted precision. Clearly, they measured the amounts present in a single tablet (of nominally 45 g) and then converted that to quantities in 100 g (a measure that's usually present in such tables of nutritional information, probably so that you can compare quantities of nutrients in different items regardless of the typical serving size of each), always representing them as numbers with one decimal place.

This means, for example, that the tablets supposedly contain "4'444.4 µg" of folic acid per 100g.

Really? Is that really accurate to the nearest 100 nanograms?

I'll note that the quantity per tablet is "200 µg", which is presumably "2×10² µg" and not 2.00×10² µg, let alone 2.0000×10² µg with five significant figures, as implied by the quantity per 100g.

I also note that the tablets contain "2.0 mg" of vitamin B6 but "1 µg" of vitamin B12, implying that they were aware of precision there—yet those two measurements turned into 44.4 mg and 22.2 µg, respectively, both implying three significant figures. (And a precision accurate to the nearest 100 nanograms in the second figure, again.)

Honestly, people. Learn about the difference between precision and accuracy, and don't claim more precision than is warranted by the accuracy.

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