Kalim Wants to Study the Effectiveness of a New Teaching

Multiple Choice

Kalim wants to study the effectiveness of a new teaching method. He includes two teachers of a class in the experiment. One teacher uses the new method of teaching, and the other teacher uses the old method. At the end of the semester, he finds that students who were taught in the new way had higher grades than students taught in the old way. What is the confounding variable?

A) Grades
B) Teaching method
C) The two teachers
D) The class