> > "We found no reliable evidence that abstinence prevents teen pregnancy" > > "We examined whether promoting abstinence prevents teen pregnancy and the resul

> > "We found no reliable evidence that abstinence prevents teen pregnancy" > > "We examined whether promoting abstinence prevents teen pregnancy and the results were inconclusive" > The first is obviously wrong, No. They're equivalent. They both mean "we looked, and we didn't find any confirming evidence." You're confusing "we found no reliable evidence of X" with "we found evidence of NOT X", which is different, and essentially never achievable in empirical studies (note: this is not an invitation to get side-tracked in pedantic debates about proving the null; I'm telling you how actual randomized controlled trials work, in real life.) Proving a negative via statistics is ~impossible, so what you do instead is to look for significant differences in X, attributable solely or partially to the intervention. If you don't find such a difference (as was the case in the mask review), you say "we found no reliable evidence of X". But when the Cochrane authors wrote "Wearing masks in the community probably makes little or no difference to the outcome of influenza‐like illness", they really did mean exactly what it sounds like -- the effect size in an aggregated pool of randomized controlled trials was statistically indistinguishable from zero. You can debate whether or not they looked for the right thing (X), you can debate whether or not adding another big randomized trial would help find X, and so on. But the plain-text interpretation is correct.