  When deploying online homework in physics courses, an important consideration
is how many attempts should be allowed in order to solve numerical
free-response problems. While on the one hand, the maximum number of attempts
should be large enough to allow learners mastery of the concepts and
disincentivize copying, on the other hand, too many allowed attempts encourage
counter-productive problem-solving behavior. In a study of an introductory
calculus-based physics course for scientists and engineers which had different
numbers of allowed attempts in different semesters, it was found that except
for the initial tries, students are not making productive use of later
attempts, and that in fact higher numbers of allowed attempts lead to less
successful homework completion.
