Answer:
20 students
Step-by-step explanation:
Sample is basically a selected subset of a population. A researcher is investigating the effect of sugary cereal on the aggression of second graders during morning play period. For this purpose, a researcher selected 20 student and feed them a sugary cereal and then observe their behaviors. Here, 20 student are selected from the all second grader students. So, the sample in the conducted study are 20 students.