The common student error in the question below is somewhat predictable – but I’m not sure why the students make the error that they do.

Whilst 60.4% of responses are entirely correct, 21.7% select the three options that are actually the places where the function rather than its derivative is zero. In the existing version of the *Maths for Science* End of Module Assignment, this question is assessing the contents of a chapter that some students choose not to study – so it is more than usually likely that a certain percentage of students are guessing, further encouraged by the fact that this is a multiple choice question.

So I’m not sure we can draw many conclusions from the errors that students make on this occasion. But if students really think that dy/dx is zero at the points where the graph crosses the horizontal axis, then they are mistaking the function and its gradient. This is a pretty basic mistake – perhaps a bit like mistaking x to the power of 3 with x times 3. That might be rather interesting.

Pingback: e-assessment (f)or learning » Blog Archive » Converting radians to degrees