Another good reason never to answer questions on tests -- as if you needed one

At the AP physics reading, I graded problem B3, about single slit diffraction.  The rubric will be released in September -- suffice it to say that the student who did everything right but incorrectly treated the plates as a double slit could get all but two points.

Once every few hundred exams I would see a comment to the effect of "If this was supposed to be Young's experiment, it is lacking an extra slit to allow constructive and destructive interference between the waves."  Okay, these students missed the point -- even single slits show a diffraction pattern, and it's a common misconception to think otherwise.  Certainly more than just those who expressed their bafflement in writing shared this lack of understanding.

The key to success on a physics test, and, I believe, the key to thinking like a physicist, is how a student reacts to such a conundrum.  "The question doesn't seem to make sense.  What do I do?"  What do we *want* our students to do?

The ideal reaction is to write the issue as the student sees it.  "This sure looks like an interference problem, but how can interference happen with a single slit?"  And then, to attack the problem somehow, someway:  "Well, I'm going to treat this like a double slit anyway and see what happens."  I saw students using just this approach, and doing well.

The poor reaction is for a student to become offended and huffy: "Single slits don't diffract.  What the heck do you want me to do, then?"  "My teacher never taught me to do single slits.  Can you call my school and get him fired?"  "What a dumb question.  We never studied this, just double slits."* 

*Note that these are not verbatim student responses, just general impressions of things students have written.

It's easy enough for me and my physics teaching friends to get haughty about the poor reaction.  Damn fool kids these days, they don't study, they don't listen, etc.*  But never forget that it is our responsibility not just to teach the material, but to prepare our students for a comprehensive exam.  The students who fight through their initial confusion to get substantial partial credit weren't necessarily smarter than the rest, but they likely had been prepared for just this sort of situation.

*Kids in our day studied, listened, respected their elders, and never texted in class.

Consider how your students might react to this question on an in-class test.  Early in the school year, every student in America would want to come to the teacher's desk to say, "shouldn't this be a double slit so there can be interference?"  Our job as physics teachers is to prepare the students to have their ability to ask questions eliminated.  It's a physics test, not a test of how well you can read the teacher's face or coax information out of him. 

I talk to my classes BEFORE our first test of the year, explaining how to handle just this sort of situation.  Still, they will try to ask questions during the first test, and it's likely they will make me very angry.*  The class learns that I mean business -- they have to figure out test questions on their own.

*While I am always a loud guy, the only times I will become truly *angry* at a student might involve blatant disrespect,, laziness combined with arrogance, or ignoring my rules about questions during tests.

I would bet that many of the folks who became upset about the single slit were frustrated because they were used to convincing their teacher to talk them through difficult questions, and that couldn't happen on the AP exam.  You and I can't possibly teach well enough that every student is fully comfortable on every question.  But by testing regularly under authentic conditions, and then debriefing after each test, it is possible to train our students how to react when they're not comfortable.  That's a skill that our graduates will thank us for someday.

GCJ

The Jacobs Crusade – NO QUESTIONS DURING A TEST!!!

I refuse to answer questions during a quiz, test, or exam.

Why am I so cruel, you ask? Or, at least, students, parents, and colleagues ask. Thing is, by mid year, no one complains about the “no question” rule. And my colleagues are occasionally envious.

I want to know what my students can do on their own. Daily interaction and coursework provides plenty of opportunities for students to talk to me and to each other, to figure out how to approach the types of problems the class covers. The purpose of a test is for my students and me to see how successful they have been in learning the material. And I can’t effectively evaluate my students or my teaching unless I get an authentic account of each student’s ability.

Think about what kinds of questions students tend to ask during a test…

-- “What is this question asking for? How do you want me to answer?”

This student may be truly confused by the wording of the question; or, the student could be stuck and hoping for a hint. Either way, this is an inappropriate question. I make sure that homework problems are worded in the same style as test problems, so that there should be no surprises on the test. Homework is the time to learn vocabulary, and to get in tune with “what the problem wants you to do.” And if the student is stuck, well, then the test has served its purpose – it’s exposed a portion of the course that the student does not understand yet.

Besides, how am I supposed to answer this? Tell him to read the question again? Or, am I supposed to just solve the problem for him? I don’t think so.


-- “You didn’t give us enough information to solve this problem.”

Well over 90% of the time when this question comes up, the test problem is just fine… it’s that the student is approaching the problem incorrectly. For example, in a conservation of energy problem, the mass term often cancels; an object’s mass is not a necessary piece of information. Recognizing that the mass cancels is a physics skill, one that I often test. But if students are allowed to ask why I didn’t give them the mass, then part of the purpose of the test problem is eliminated!

So what about that rare instance when you should have given an object’s mass, but didn’t? Shouldn’t people be able to ask about that?

No.

Before the first test of the year, I prepare my classes for just this kind of situation. I tell them that if they think I screwed up by not giving them critical information, then they should tell me so in writing on the test… then they should continue solving the problem by making up a reasonable value. There’s nothing wrong with someone writing, “You didn’t tell us the mass of the roller coaster! So, I’m going to pretend it’s 500 kg.” This student will be in good shape… even if he was supposed to solve for the mass some other way, he can still get partial credit for finishing the problem. And, if I truly screwed up, then he’s demonstrated enough knowledge to earn full credit. Most importantly, he hasn’t distracted the entire class with his question.

-- “You made a typo here. You said, ‘find the nass of the roller coaster.’ Did you mean ‘find the mass of the roller coaster?’ ”

This sort of question makes me livid. Do you want me to take off every time your writing is unclear, or every time you make a minor grammatical error? You distracted the entire class for the express purpose of saying, in effect, “Na na na na boo, boo, teacher screwed up!”

Once again, pre-test preparation can prevent this sort of one-upsmanship. Make it clear from day one that you don’t mind any sort of WRITTEN comment on the test. If a student wants to write how awful a question is, or to criticize my spelling or syntax, more power to him, as long as he does it in writing. In fact, I often give long, detailed, polite responses to reasonable criticisms written on a test.

Most importantly, of course, if the student happens to be right about a poorly worded or ambiguous question, I’ve got to be fair in my grading. Once in a long while I just throw out a part of a question, or give a huge variety of answers full credit, because I realize later that the problem wasn’t good to begin with.

In fact, just today someone told me (after the test was over) that multiple choice question #18 included two identical answer choices. It turned out that those choices were wrong, so no one cares. But if the identical choices had been correct, I would have at least counted either choice right, and possibly thrown out the entire question because of the confusion my mistake caused.

But no one asked during the test. All of my students got 120 minutes of silence in which to do their work. I got some grading done. This time of year, if I’ve done my job right, a trained orangutan could administer my tests. And that, I think, is the way things should be in high school.