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Why do profs give exams like this?

by gravenewworld
Tags: exams, profs
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flyingpig
#19
Nov21-11, 06:51 PM
P: 2,568
I've had those on online assignments, but never exams. Personally I've always thought T/F were the toughest (at least with my professors). Most of what I've had are "If True, explain why. If False, give a counterexample. DO NOT CORRECT THE STATEMENT"

And Physics M/C are funniest because you can just use dimensional analysis lol
Vanadium 50
#20
Nov21-11, 07:00 PM
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Quote Quote by Hurkyl View Post
And yes, you really do want to penalize guessing. Admitting you don't know how to do a problem is a much, much better response than making a blind guess.
I had a professor once who took 15 points off a 10 point problem. "If you kept your moth shut, I wouldn't know if you knew anything or not. But once you started writing...."
gravenewworld
#21
Nov21-11, 11:11 PM
P: 1,408
This was for a med school genetics exam.



Too many people failed it and they already sent out an email explaining that they have to now regrade the exams with partial credit for the questions that required multiple answers. I don't understand why professors make it so difficult on themselves and stress out their students so much. It should have been clear before the exam was given that grading a test in a all or none fashion for many questions was set up for failure for many students.
DrummingAtom
#22
Nov21-11, 11:35 PM
P: 661
I'm also frustrated with multiple choice exams. I'm taking physics 2 (E&M) currently and it's 100% multiple choice questions for the tests. Most of the time I can get away with analyzing the answers like flyingpig said with dimensional analysis. The tests are 20 questions. The last test tripped me up with some negative signs; in my last physics class I would have gotten docked some points but not the entire question.
dacruick
#23
Nov22-11, 07:53 AM
P: 1,084
Quote Quote by Hurkyl View Post
That's not bad enough. If you want to penalize guessing, the expected value of a guess must be less than that of leaving the question blank.

And yes, you really do want to penalize guessing. Admitting you don't know how to do a problem is a much, much better response than making a blind guess.
Maybe it depends on the subject. I am currently pursuing a bachelors degree in physics, and a multiple choice question in physics is cruel enough already. With all the work involved, to either get perfect or a negative score seems foolish.

Aside: Do you think long answer questions should penalize guessing too?

And many on this thread keep mentioning that knowing that you don't know how to do a problem is better than guessing, which I agree with. But you fail to mention when students make a mistake. If a student knows how to do a problem, gets a sign switched up, their 5/5 just turned to -2/5? Thats pretty ridiculous, and IMO, an inappropriate way to test physics material.
xdrgnh
#24
Nov22-11, 11:38 AM
P: 315
Quote Quote by Vanadium 50 View Post
I had a professor once who took 15 points off a 10 point problem. "If you kept your moth shut, I wouldn't know if you knew anything or not. But once you started writing...."
Lol so people like Newton who made mistake and didn't know something should be penalized more for there mistakes rather then praised for there accomplishment.
Number Nine
#25
Nov22-11, 12:55 PM
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Quote Quote by xdrgnh View Post
Lol so people like Newton who made mistake and didn't know something should be penalized more for there mistakes rather then praised for there accomplishment.
...what?
vela
#26
Nov22-11, 02:33 PM
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Quote Quote by dacruick View Post
Maybe it depends on the subject. I am currently pursuing a bachelors degree in physics, and a multiple choice question in physics is cruel enough already. With all the work involved, to either get perfect or a negative score seems foolish.
It depends on the course, not only the subject. If you're teaching two 300-student sections of lower-division intro physics, the appeal of using multiple choice questions is obvious.
And many on this thread keep mentioning that knowing that you don't know how to do a problem is better than guessing, which I agree with. But you fail to mention when students make a mistake. If a student knows how to do a problem, gets a sign switched up, their 5/5 just turned to -2/5? Thats pretty ridiculous, and IMO, an inappropriate way to test physics material.
Students will, obviously, make mistakes, but that alone is not reason enough to write off the use of MC exams altogether. A good MC test consists of a large number of independent questions, so that the effect of a single mistake is limited. A few mistakes here or there, you can chalk up to random chance. Errors on a significant fraction of the questions, however, likely indicate a student doesn't know the material well.

The main reason I haven't liked using MC exams is because, frankly, they're more difficult to write. It's a lot easier to come up with a small collection of free-response questions rather than a large number of good MC questions with plausible wrong answers.
mathwonk
#27
Nov22-11, 02:56 PM
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Although the analyses by instructors here of the value of different types of questions is useful, the intent of this thread seems misguided. instead of griping about how many points your wrong answers are worth, you should be focusing on getting them right. only weak students fume about scoring.

i once took 3 high school physics tests in one day, (to make up work after being absent) that were all multiple choice and I got two 100's and one 97. Yes the tests were stupid, but my response was just to nail them, all but one question. Moreover the only question I am proud of was the 3 point one I missed.

It asked what fraction of the sun's light is received by the earth, a number that had been mentioned in the book without explanation. I calculated the surface area of a sphere whose radius is the known distance from the sun to the earth and divided it into half the surface area of the earth, which was wrong. Do you see why I should have used the area of a plane section through the center of the earth?

Now you are right that this story illustrates the potential weakness of (poorly written) MC tests, but when I explained my answer to the prof and asked why it was wrong, I got his respect since my creative wrong solution was more impressive than a memorized correct one, and his explanation got some from me. That was far more valuable than the 3 points, which I did not complain about losing. Someone who argues points unfortunately tends to come off as a whiner.
Jolb
#28
Nov22-11, 03:11 PM
P: 419
To the OP,

There could be good reasons for why you would want this type of exam. For example, it might be crucial to the subject that you know exactly the right answers and can determine what the wrong answers are.

Example:(From a math class exam)

What is (are) the cube root(s) of 1?

a) 1
b) i
c) e^(i*pi*2/3)
d) e^(i*pi*4/3)



A question like that shows that if you just pick a, you don't understand the question, and if you pick a, b, c, and d, you're making a really careless mistake. Chances are if you can get c, you won't miss d (or vice-versa), and if you do, you're missing the very important fact that there are always n nth roots of one.

Another example (From a US history exam):

Who of the following was (were) president(s)?
a) Benjamin Franklin
b) Alexander Hamilton
c) Thomas Jefferson
d) James Madison

In US history, it's important to know the presidents! You should know c and d, and the inclusion of a and b is testing whether you have the common misconception that they were presidents (since they're on dollar bills).
Theorem.
#29
Nov22-11, 03:31 PM
P: 237
Quote Quote by mathwonk View Post
Although the analyses by instructors here of the value of different types of questions is useful, the intent of this thread seems misguided. instead of griping about how many points your wrong answers are worth, you should be focusing on getting them right. only weak students fume about scoring.

i once took 3 high school physics tests in one day, (to make up work after being absent) that were all multiple choice and I got two 100's and one 97. Yes the tests were stupid, but my response was just to nail them, all but one question. Moreover the only question I am proud of was the 3 point one I missed.

It asked what fraction of the sun's light is received by the earth, a number that had been mentioned in the book without explanation. I calculated the surface area of a sphere whose radius is the known distance from the sun to the earth and divided it into half the surface area of the earth, which was wrong. Do you see why I should have used the area of a plane section through the center of the earth?

Now you are right that this story illustrates the potential weakness of (poorly written) MC tests, but when I explained my answer to the prof and asked why it was wrong, I got his respect since my creative wrong solution was more impressive than a memorized correct one, and his explanation got some from me. That was far more valuable than the 3 points, which I did not complain about losing. Someone who argues points unfortunately tends to come off as a whiner.
Mathwonk,
I definitely agree with you that a creative response that may be wrong is much more valuable then a regurgitation of memorized material. The fact that you tried to construct an answer using your knowledge of the subject illustrates your strength as a student (when you were a student). I myself have ran into at least a few situations where I have provided a creative proof, that was original in the sense that I had never seen it before, in order to answer an examination question. Although it did suck when i found out I had missed a small step or gone astray somewhere, loosing the marks never compared to the insight I gained. Of course, I would not recommend any student always try to do such a thing on an exam, but they should not be put back when the effort was put and they did not get the marks. Sometimes I still get upset, especially when I have found out a friend or colleague has received the full marks for providing nothing original (it is hard not to get upset sometimes!). There are many exam's I have written that were trivial in the sense that they required little "original thinking", and although I have performed well on such exams, I never find myself particularly proud of doing so as I have not really demonstrated anything special.
mathwonk
#30
Nov22-11, 04:53 PM
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Theorem, you are indeed kind to look for the good in my response. To the OP, it dawns on me occasionally also that i am getting a bit grumpy and preachy in my dotage.

You are right that a teacher should consider what it is he/she is actually measuring with his questions/scoring. I agree too that you might ask yours the rationale behind the one you question. Like mine, he may have something to say that you will learn from.

In my case, I had arrogantly thought my teacher was an idiot until he showed me he really did know how to deduce the answer to the one I missed. Then I realized he was just not exhibiting his knowledge to us, perhaps assuming we would not appreciate it.
Andy Resnick
#31
Nov23-11, 07:40 AM
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Quote Quote by mathwonk View Post
<snip>
You are right that a teacher should consider what it is he/she is actually measuring with his questions/scoring. <snip>
I could not agree more; I would only add that the teacher should *clearly* communicate their metric/rubric to the students.

There are lots of things that can be measured with any test: factual knowledge, reasoning ability, creativity, communication skills and the ability to deal with a stressful situation are a few. By selecting a particular format, the instructor also chooses to focus on one or a few of these.
Jack21222
#32
Nov23-11, 08:15 AM
P: 772
Quote Quote by Hurkyl View Post
And yes, you really do want to penalize guessing. Admitting you don't know how to do a problem is a much, much better response than making a blind guess.
I strongly disagree with this. If a student is able to eliminate choices, that demonstrates some knowledge of the subject, and should have a positive expected value.


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