There is a very common fallacy called, "hasty generalization." Basically, it says it is illogical to assume something happens all the time, everywhere, just because you've seen it once, or a few times.
The fallacy is illustrated in this common joke.
An engineer, a scientist, and a mathematician were riding a train into Ireland. As they observed the passing vista, they saw a black sheep. The engineer commented, "Interesting, that the sheep in Ireland are black." The scientist corrected him, "Let's not generalize too hastily. At least one sheep in Ireland is black." The mathematician thoughtfully added, "No, at least one side of one sheep in Ireland is black."
We all generalize hastily without knowing that we are. But in some cases, the fallacy is rather obvious. Take the case of global warming. Physicist Freeman Dyson recently commented on generalizations, not only from regional warming, but also from inadequate computer models that do not represent the true dynamics of the planet.
Freeman Dyson Takes on the Climate Establishment