Nico wanted to determine the number of students in his school who buy school lunch he walked around the cafeteria one lunch. Looking to see whether every fifth person in the cafeteria purchase lunch or bought their own

You probably are looking for which type of study was conducted by Nico to collect the dа ta:

There are basic two types of studies to collect the dа ta:

a) Observational Study

b) Experiment

In experiment, some treatments are applied to a group and effects are noticed and recorded. In observational study, no treatments are applied and the subjects are observed to collect the data.

In this case, Nico is just observing the students as he walked around the cafeteria, so the type of study involved to collect the data is observational study.