Nico wanted to determine the number of students in his school who buy school lunch. He walked around the cafeteria one lunch period looking to see whether every fifth person in the cafeteria purchased lunch or brought their own. Which method did he use to collect his data?

Nico watched students and recorded whether they bought lunch or brought their own, without asking them questions or changing anything about their lunch. Collecting information by watching people’s behavior is an observational study. A survey would involve asking students questions, and an experiment would involve changing a condition.

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