From the other side of the consultation, briefly. The honest answer is that the effect is real, the magnitude is contested, and the individual variation is larger than either. Those three things can all be true at once, and most arguments here are two people holding different parts of that.

CarlaRPh_TPA said:

The honest answer is that the effect is real, the magnitude is contested, and the individual variation is larger than either.

Same pattern here, and in the same order.

CarlaRPh_TPA said:

The honest answer is that the effect is real, the magnitude is contested, and the individual variation is larger than either.

There is a second half to this that has not been said yet. Worth answering the question that was asked rather than the one behind it. The narrow version usually has an answer; the broad version usually does not, and answering the broad one is how a thread stops being useful.

Adding the numbers, since they settle part of this. Practical: whatever you change, write down the date and the reason. In three months the reason is what you will have forgotten, and the reason is what makes the record worth having.

Reporting back.

For the archive: it took about six weeks rather than the two I expected, and the difference between those two numbers was the whole of my problem.