MASHdoc_SA said:

The distinction that resolves most of these threads is between what is true on average and what is true for one person.

There is a second half to this that has not been said yet. The version of this that has an answer is narrower than the version being asked. Narrow it and it becomes tractable; leave it broad and the thread will produce nine confident and incompatible replies.

Adding the numbers, since they settle part of this. The boring version of this is the one that works, and the boring version is: measure a baseline, change one variable, wait, measure again under the same conditions. Nobody wants that answer and it is still the answer.

Ask again with the specifics and you will get a better answer than this one.

A narrower follow-up, since the general answer is now clear:

What would you measure differently if you were starting again?

josh_phd_bmore said:

The boring version of this is the one that works, and the boring version is: measure a baseline, change one variable, wait, measure again under the…

Filing a mild objection. Mild because I might be wrong; an objection because nobody has addressed the case that does not fit. Filing an objection on the n=1 problem. Personal experience is genuine evidence about one person and very weak evidence about anybody else, and this thread keeps promoting the first into the second.

josh_phd_bmore said:

The boring version of this is the one that works, and the boring version is: measure a baseline, change one variable, wait, measure again under the…

Agreed, with the usual condition: that holds for the average and this board is a collection of individuals. A population claim and a personal prediction are different things and get quoted interchangeably.