A study of class payments for a local art studio found that individual painting classes students paid for directly had a cancellation rate of less than five percent, while those who signed up in advance for a twelve-class package had a cancellation rate of more than 25 percent. This might have been caused at least partially by the fact that the more aware students are of the cost of a course, the higher the chance that they will attend.
Which of the following would, if true, best serve as an alternative explanation of the results of the study?