Your instructor gives a 60-item pretest on the first day of your statistics class. Because there has not yet been any statistics instruction, most students score quite low on the test. However, a small number of students have had statistics instruction as part of another course. These students do very well on the test.

What measure of central tendency (centrality, average, or middleness) best summarizes the entire class's statistical knowledge at the start of this course? Why? Please explain your answer.