What reasoning error describes the assumption that all people who fit a certain group must have similar attributes?

The reasoning error that describes the assumption that all people who fit a certain group must have similar attributes is known as division. This error occurs when one incorrectly applies the characteristics of a whole group to an individual member of that group. For example, if a person believes that because a certain sports team is known for a strong work ethic, every player on that team must also possess a strong work ethic, they are committing the division fallacy.

It's important to note that while groups may exhibit common traits, this does not necessarily mean that every individual within those groups shares those traits. Recognizing this distinction helps avoid overgeneralizations that can lead to stereotypes or misconceptions about individuals based solely on their group identity.