The math center coordinator at a college wants to show that the center helps students get better grades in math classes. Two weeks after the semester is over, she researches students’ grades and finds that a greater proportion of students who attended the math center passed their math classes that semester than those that did not attend the center. The person concludes that the center helps students get better grades in math classes.
a. Describe the problems with the coordinator’s study. Include in your description at least one possible lurking or confounding variable.
b. Redesign the study so that it is a well-designed experiment.