newstart_MO said:

There is a difference between no evidence and evidence of no effect, and this subject is one where the two get swapped freely in both directions.

Second this.

OP back with an update, since a thread like this is useless without one.

Late follow-up. I did not do what was suggested, I did something adjacent, and it worked; posting the difference in case it matters to somebody.

One concrete data point for the thread. One habit that pays for itself: post the method alongside the number. A figure without its method cannot be checked, and an unchecked figure is how this community accumulates folklore.

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:

Was that from a primary source or from a summary of one?

Old thread, but it comes up first when you search for this, so it is worth updating. 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.