An anonymous donor cashes in a $30 donation to ask:
Homework solutions from intro physics through grad school physics are available online, and while working through Jackson and Goldstein problems can be miserable without some guidance, the temptation is there to plagiarize. When you teach, do you use book-problems or write your own? Do you trust that those who are really interested in the subject will do the right thing and slog through homework like thousands before them?
An excellent question.
Homework is really a vexing issue. There’s no way to really learn physics without doing physics, which means that students need to do practice problems if they’re going to learn anything. There are lots of problems with this, though, starting with the fact that if you assign lots of homework problems, you need to grade lots of homework problems, and moving up through the wide variety of ways students have for making it look like they did the homework without actually doing the homework (from reverse engineering odd-numbered answers in the textbook to Googling up solutions).
How do I deal with the question of whether the students are doing the work themselves or Googling up old solutions? I deal with it by not caring about it.
I’ve spent an inordinate amount of time thinking about how to handle the homework in the intro classes, and have settled on a slightly complicated policy that I think works pretty well:
Homework and quizzes together make up either 20% or 30% of the grade, split evenly between the two. Homework is subdivided further, into two types of homework, nightly and weekly.
Nightly Homework is, as the name suggest, assigned every class, due the next class. A typical nightly assignment consists of 3-4 problems from the textbook, generally fairly straightforward plug-and-chug problems. These problems are not collected and graded, though– students are expected to do them, but I don’t check that they did.
As an incentive to do the assignment, though, roughly half of the quizzes in the term (I usually give 8-9 quizzes in the intro classes) are taken verbatim from nightly homework problems. The quiz consists of one problem, with about ten minutes allowed for solving it, and if students have done the homework, it should be trivial. I’ll also go over nightly homework problems at the start of class, for those who have questions (and I have, on occasion, been asked to do the exact problem that was about the be on a quiz. Astonishingly, some people still missed it).
The idea of the nightly homework is to encourage students to work some problems immediately, while the material is still fresh. This should help them fix the basic ideas in their minds.
Weekly Homework is, as the name suggests, assigned once a week, usually on Friday, and due a week later. These assignments consist of 3-5 more complicated problems from the textbook, and these are collected and graded in detail. I collect homework on Friday, and grade it over the weekend, returning it (ideally) on the following Monday.
After I hand the homework back, I post detailed solutions, and students have the opportunity to re-do the assignment for half the credit they lost. Thus, a student who got an 80/100 can look at the solutions and re-write the answers to raise the grade to a 90/100. The idea here is to encourage students to take a second look at the problems, and see where they went wrong, before they completely forget what the assignment was about.
I explain all this to the students on the first day of class, including the rationale for the policies, and it generally works pretty well. Most of the students appear to be looking at the nightly assignments (quiz averages are usually pretty good), and everybody hands in the weekly homework. Probably half of the students take advantage of the re-write offer at some point in the term, usually the better students in the class.
As for the question of how the work is getting done, you’ll notice that homework is 10-15% of the final grade, with quizzes making up another 10-15%. The exams (two mid-terms and a final) account for 50-60% of the final grade. The homework grade is just not that significant compared to the exams.
A student who is doing the homework and doing it well will generally do well on the quizzes and exams, and end up with a good grade. A student who isn’t doing the homework will get crushed on the exams, and end up with a bad grade, whether or not they’ve copied homework solutions to obtain a good homework grade. A good homework grade will turn a B+ into an A-, but it’s not going to make a C into an A.
As a result, I don’t worry much about whether students are doing the homework by themselves or not. In fact, I make it easy for them to not do the work, if they so choose– I encourage them to work in groups (which is an essential habit for upper-level classes), and I post the even-numbered answers on the class web page so they can check their work. I’ll go over any problem at any time (though with the weekly assignments, I usually just set the problem up, and leave the details to them), and if they ask questions in class when the weekly homework is due, I’ll allow them to hand it in later.
As a courtesy to my colleagues, I put the solutions and even-numbered answers on a password-protected page, but personally, I don’t worry about how to enforce homework discipline. Homework is for practice, to help them learn the material, not a major factor used to determine the grade.
(Upper-level classes are a different beast, but I don’ teach those as often, and the policies are less set.)