A large-scale study at the University of Georgia has found that college students provided with free course materials at the beginning of a class get significantly better academic results than those that do not.
The Georgia study, published this week, compared the final grades of students enrolled in eight large undergraduate courses between 2010 and 2016. Each of these courses was taught by a professor who switched from a commercial textbook costing $100 or more to a free digital textbook, or open educational resource, at some point during that six-year period.
Source: Measuring the impact of OER at the University of Georgia :: Inside Higher Ed
This sort of study needs to be done at the post graduate level. I’m not surprised by the results since providing OER helps reduce the cost of education, and lowers the stress of having to pay for books out of a limited budget.