Which reasoning error occurs when one makes a conclusion about a group based on an individual, such as assuming two tennis players will win based solely on their individual accomplishments?

The reasoning error that occurs when someone makes a conclusion about a group based on the characteristics or achievements of an individual is known as Composition. This fallacy arises when the characteristics of the individual are incorrectly applied to the group as a whole, leading to a flawed conclusion. In the context of the question, inferring that two tennis players will win solely because of their individual accomplishments overlooks the dynamics of team play and other factors that contribute to the success of a group rather than just its individual members.

Understanding Composition is critical because it highlights a common error in reasoning where one might assume that what applies to a part (the individual accomplishments) also applies to the whole (the group’s overall ability to win). In contrast, other errors like Division involve assuming that what is true for the group must also be true for each individual within it, while Selected Instances typically refers to drawing conclusions based on a small, non-representative sample instead of the entire population.