A hasty generalization fallacy is a claim made on the basis of insufficient evidence. Instead of looking into examples and evidence that are much more in line with the typical or average situation, you draw a conclusion about a large population using a small, unrepresentative sample.

The hasty generalization fallacy, also known as the overgeneralization fallacy, is the logical fallacy of making a claim based on a sample size far too small to support the claim. Whether a sample size is large enough to support a claim depends on the specific claim.

A hasty generalization is a fallacy in which a conclusion that is reached is not logically justified by sufficient or unbiased evidence.

A hasty generalization is a quick judgment about a big group based on too little information. It’s an assumption that’s not always right, like putting a whole puzzle together with just a couple of pieces.

In a hasty generalization fallacy, the writer or speaker makes a claim that because something is true about a sample of a larger group, it is true about the group as a whole. For example, some might say "I have dated three redheads, and they all had tempers. Therefore, all redheads have tempers."