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Grading an exam

Let’s talk tests.

I prefer taking a test over writing one, and I prefer taking a test over grading one. However, there is no better way to learn what your students know than by giving an exam. In the next POGIL blog post I will discuss how teaching using POGIL affects the dynamics of giving exams.

When writing the exam, I want to make sure I test all the material (what if the students study something and I don’t ask about that something?). I want the students to think “yes, I’ve seen that before” – so I know that I have tested them on the things I have emphasized and made the students practice. Generally these are the number-crunching questions (calculate the work done… what is the wavelength of a certain transition..). Students do well on these questions, but it takes them a long time to solve.

I also want to put in a question the students have not seen before. Why? So I can test their critical thinking skills. After all, we tell our students that critical thinking is important. If something matters, there must be points assigned.

I try to think about making the test so that the weakest students in class can get at least a 60 and so that the strongest students find something to challenge them. Sometimes this means asking students to prove something mathematically (I teach physical chemistry!), and I will often set this up as an extra credit question.

Then I have to consider the grading. My physical chemistry classes range from 60 to about 120 students, and I don’t get any assistance from TAs for grading. So I want to include some tasks that are pretty straightforward to grade. This is why I include true/false questions – easy to write, easy to grade. Not, however, easy for students.

Maybe your students, like mine, beg you for an old exam to study from. Given that old copies of our exams are likely floating around (in bits or on paper), it seems fair to give everyone in the class the same opportunity. So I post the old exam (without answers) and then I have to be even more creative to come up with different questions covering the same concepts.

This spring I’ve had the added challenge of teaching in a 50-minute class period. In a 75-minute class, the students could have a full 85 minutes to finish the exam because there is 15 minutes between classes. A 50-minute class means at most a 57-minute exam. How to cut an 85 minute exam by 30 minutes?

Spring 2017 exam 1 – perfect exam. The students finished on time (in 57 minutes), and almost all of the students worked on the exam for the full 57 minutes. The mean score was 85%. No one scored below 50%. **Success!**

Spring 2017 exam 2 – flawed exam. No student turned in an exam before 50 minutes. After 65 minutes, I walked toward the room exit announcing that any exams not in my hands would not be graded. The mean score dropped to 75%. Because my students became flustered and frustrated with the exam length, they stopped thinking (clearly). Few of them had time to review their answers. **Miss!**

*The Silver Lining*: I did find that exam 2 highlighted the concepts the students had mastered (most could plug numbers into equations, assign point groups, assign symmetry to molecular vibrations, and describe the harmonic oscillator). Even better, I learned what my students really didn’t “get”. (They do not have a good grasp of the relative energies in translation, vibration, and rotation, and they have trouble manipulating equations symbolically.)

Coming soon: Spring 2017 exam 3: Return to this site in May to find out if exam 3 was a success or a miss.