Final answer:
Michelle is assumed to be from California due to her characteristics, which align with the representative heuristic, where people judge based on typical examples rather than statistical reality.
Step-by-step explanation:
The assumption that Michelle is from California based on her hair color, enjoyment of the summer, and fondness for the beach is best explained by c) Representative heuristic. This is a cognitive bias where people classify someone or something based on how similar they are to a typical case. Despite the statistical likelihood given the high percentage of in-state students, other students are swayed more by the stereotype of a Californian than by the data about the university's demographics.
Confirmation bias would involve seeking out or interpreting information in a way that confirms existing beliefs, while stereotype threat is the fear that one will confirm an existing stereotype about their group, which can affect behavior and performance. Prejudice refers to preconceived opinions not based on actual experience. In this scenario, it is the representative heuristic driving the assumption because fellow students are guided by the representational image of a Californian that matches with Michelle's characteristics.