Consider again the example used in Exercise 16.54.

As before, the researcher is interested in predicting mathematics ability with the ultimate goal of identifying ways to improve mathematics performance. If you were to develop a multiple regression equation instead of a simple linear regression equation, what additional variables might be good independent variables? List at least one variable that can be ma -

nipulated (e.g., weeks of tutoring) and at least one variable that cannot be manipulated (e.g., parents’

years of education).