Comment on “Benefits of completing homework for students with different aptitudes in an introductory electricity and magnetism course”

In a recent study, Kontur, de La Harpe, and Terry [1] carried out an important study examining the differential benefits of doing more homework on different levels of students. Their surprising results, which suggest that doing homework does not benefit lower aptitude physics students, prompted us to examine the correlation between homework and exam grades in our own courses. In contrast to their findings, we see a correlation between homework and exam performance for all our students, with it being clearest for the lower aptitude. This emphasizes the need to examine questions about the benefit of homework carefully, recognizing the possible differences within and across different institutional populations and courses; a sentiment also conveyed by Kontur, de La Harpe, and Terry. Here we present data from two University of British Columbia (UBC) first-year physics courses. UBC is a large, relatively selective, public research university, and these courses are similar to those at many comparable institutions. One course is the introductory calculus-based electricity and magnetism course P102 (N 1⁄4 514) taken by essentially all science and engineering students, quite similar to the course Kontur, de La Harpe, and Terry analyze. The second course is algebra-based introductory mechanics P100 (N 1⁄4 744) taken primarily by a diverse group of students that did not take physics 12 in high school (60% science, 15% arts, 25% other majors). We include the latter here for comparison of the overall correlation between homework and exam scores, and in particular to see if there was a strong dependence on the exam format. The algebra-based mechanics course P100 has open-book-and-notes midterm and final exams, and so students have similar resources available as for the homework, while the electricity and magnetism course P102 has closed-book exams in which only one sheet with formulas is allowed. Otherwise, the homework and grading was the same between the two courses, with homework counting for 10% of the course grade. Unlike the sample of Kontur, de La Harpe, and Terry, these courses are taken by less than half the UBC student population. For the analysis of our data, we use a similar method as Kontur and co-workers. We use the Mastering Physics overall score as a measure for homework completion. In our courses, the default grading policy of the Mastering Physics software was modified to a more lenient due date policy (−10% for each day late with a maximum 50% penalty). For the exam score, we use the combined grade of midterm tests and the final examination, weighted as in the course grade of 1=4 and 3=4, respectively, for the electricity and magnetism course P102. The respective weights for midterms and final examination were 1=3 and 2=3, respectively, for the algebra-based introductory mechanics P100. We find a much stronger correlation between exam and homework performance for both courses than what was reported by Kontur, de La Harpe, and Terry. Figures 1(a) and 1(b) show the data for all students. The trends are similar in the two courses, but the correlation between homework and exams is stronger in the case of P102 (r 1⁄4 0.28 versus 0.18). Note that P100 has open-book examines, but, perhaps somewhat surprisingly, lower correlation. Possible reasons are discussed below. In Figs. 2(a)–2(d) we show the data from P102 broken down by aptitude quartile, as in Fig. 1 in the study of Kontur, de La Harpe, and Terry. Our aptitude breakdown is based on the students’ overall GPA at the end of term 1, just before starting P102. There is a strong correlation between this term 1 GPA and P102 exam performance, with an r of 0.50. This is a slightly different aptitude calculation than Corresponding author. [email protected]