Ultrasound and skinfolds: operator dependence in practice

Ultrasound and skinfolds: operator dependence in practice — setting out what I have, and where I think it stops being reliable.

Trying to establish the boundary conditions on ultrasound and skinfolds. The general claim is fine; I want to know where it stops holding, because that is where I am operating.

Three edge cases below, in increasing order of how far outside the usual range they sit.

The most useful protocol is the one you will actually repeat identically. An imperfect measurement repeated consistently beats a better one repeated carelessly.

On reflection I would soften that slightly.

Reading back through the ultrasound and skinfolds threads from last year, the same three questions come up every time and only one of them has ever been answered properly. That seems like a documentation gap rather than a knowledge gap.

Helpful, and short, which on this subject is harder than long.

Narrowing post #48, because the general version has more than one answer.

Worth stating the null on ultrasound and skinfolds before we explain it: the observation may be nothing. That possibility deserves a sentence and usually does not get one.

Where I part company with post #54, and it is a narrow parting.

Photographs under fixed lighting and posture are a genuine record and are the hardest of these to standardise.

Posting my ultrasound and skinfolds numbers with the method attached so they can be discounted properly. Uncontrolled, unblinded, and collected by someone who wanted a particular answer.

Fine by me. I had wanted a stronger conclusion and there is not one available.

This follows post #63 rather than contradicting it.

The useful distinction on ultrasound and skinfolds is between what was measured and what was inferred from it. Both end up in the same sentence and only one of them has error bars.