If the price of a textbook rises and then students purchase fewer textbooks, an economic model can show a cause-and-effect relationship only if which of the following conditions holds:
A) students' incomes fall.
B) tuition decreases.
C) the number of students increases.
D) everything else is constant.

Question

Quizplus · Accepted Answer

In order for an economic model to show a cause-and-effect relationship between the price of a textbook and the number of textbooks purchased, all other factors must remain constant. This means that students' incomes, tuition, and the number of students cannot change in order to isolate the effect of the change in textbook price. Therefore, choice D is the best answer.

If the Price of a Textbook Rises and Then Students