What is the independent variable ?

What is the dependent variable?

In a longitudinal study of attitude toward statistics, a doctoral student surveyed 20 doctoral students four times during their program: (a) before taking any statistics courses; (b) after having taken one course; (c) after all required statistics courses and (d) one semester after completing their preliminary examination. In each instance, alternate forms of the Attitude Towards Statistics instrument were used. He wants to know if doctoral students' attitude toward statistics was different at the different stage during their program.