Studies and Statistics
Aquinas famously said: beware the man of one book. I would add: beware the man of one study.
For example, take medical research. Suppose a certain drug is weakly effective against a certain disease. After a few years, a bunch of different research groups have gotten their hands on it and done all sorts of different studies. In the best case scenario the average study will find the true result – that it’s weakly effective.
But there are also about 5 studies that find that the drug is very good, and 5 studies missing the sign entirely and finding that the drug is actively bad. There’s even 1 study finding that the drug is very bad, maybe seriously dangerous.