"There is a one in 1,000 chance that the measurement is a statistical coincidence", grammatically, presumes the measurement which did in fact occur and says som

"There is a one in 1,000 chance that the measurement is a statistical coincidence", grammatically, presumes the measurement which did in fact occur and says something about the chance that a statistical coincidence did, in fact, happen. It's P(hypothesis | data). This is a classic no-no in science writing. "There is a one in 1,000 chance that the measurement would arise by statistical coincidence" uses the conditional, (implicitly) presuming a hypothesis and saying something about the chance that, under that hypothesis, such a measurement as occurred would occur. It's P(data | hypothesis).