Leaping to a conclusion

When a conclusion is drawn about all or many instances of a phenomenon on the basis of one or a few instances of that phenomenon.

For example, one may generalize about all people or all members of a group from what one knows about just one or a few people:

1. If one meets a rude person from a given country X, one may suspect that most people in country X are rude.
2. If one sees only white swans, one may suspect that all swans are white.
3. These two tools are blunt. The whole box of tools must be blunt.
4. Oxygen and hydrogen are gases at room temperature. Therefore water (H20) is a gas at room temperature.

This seeks to use inductive reasoning, but does so falsely, generalizing when there is no sound rationale for doing so. This is the basis of stereotyping, which is a Composition fallacy.

The generalization that is taking place may be due to sloppy thinking or may be a deliberate way of seeking a general rule (which may then be applied deductively elsewhere).