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.

Nico is watching students and recording whether they bought lunch or brought their own. He does not assign students to a group or change what they do, so this is an observational study. A survey would involve asking students questions, while an experiment would involve introducing a change or treatment.

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