Hasty Generalization

The fallacy of judging a large whole based on a small sample. For example, over the course of a few weeks, Kim is treated rudely and inconsiderately by a few people who happen to be wearing green t-shirts. Kim concludes that people who wear green t-shirts are rude and inconsiderate, and vows to avoid them in the future.

Or, Susan decides to watch an episode of a popular sci-fi series to see whether or not she likes it. After watching one episode, she concludes that the show is absolutely horrible and refuses to watch any more of it. But in actuality, Susan actually watched the absolute worst episode in an otherwise-good show.

Or, James and his friends have all been cheated on, lead on, and abused by their ex-girlfriends. After an evening of swapping stories about their horrible girlfriends, James and his friends come to the conclusion that all women are all disloyal, abusive, and cruel.

A more complex form of Hasty Generalization frequently pops up in fandoms, where an observer will mistake the views and actions of separate parts of the fandom as views and actions of a cohesive whole. For example, Bob sees a discussion thread where people are petitioning for a new feature in the next update of a game. A few weeks later, he sees another thread where people are complaining about the new feature. Bob responds to the thread, "Do you want this or do you not?! Make up your minds!" But in reality, the people who are complaining about the new feature are an entirely different set of people from those who wanted it.

In another example of this type of thinking, let's say the fandom of a popular TV show is generally known for having liberal and progressive views. Eventually, the work introduces a heavyset (well beyond Hollywood Pudgy) character. Soon after, a fan posts that xe thinks this character is a poor role model because said character is fat. Cue a lot of very angry people rushing forward to calk the fandom as a whole hypocritical because of this single member’s post... never mind that the original poster was never part of the progressive and liberal section of the fandom to begin with!

Those who have formed their beliefs based on Hasty Generalizations may use Observational Selection in order to maintain them and avoid critically examining them.