A scientist is investigating the hypothesis that taking more math classes in college directly leads to higher income later in life. He follows 100 students chosen randomly from the students at Valinor College, obtaining data on how many math courses they took and their annual income 10 years after graduation.

1. Briefly explain why it would not make sense to complete a t test comparing the number of math classes taken and the income ten years later.
2. The experimenter notices after the experiment that students who took more math classes also took more units in general, compared to other students. Briefly explain why might that be a problem when analyzing the experiment.