After reviewing the results of a math test, the teacher tells the class that those students who completed their review worksheets scored an average of 10 points higher on the test than those students who did not complete their review worksheets. Which of the following BEST describes how the teacher likely came to this conclusion?
A. The teacher conducted an observational study by comparing the performance on the test of those who completed their review worksheets to those who did not
complete their review worksheets.
B. The teacher conducted a sample survey by asking students if they completed their review worksheets and if they think they did well on the test.
C. The teacher performed a controlled experiment in which one group of students decided not to complete their review worksheets and the other group decided to
complete their review worksheets.
OD. The teacher performed a random experiment in which the test scores of one group of students would be higher and the test scores of the other group would be lower.