I've heard that on these types of exams you should not guess unless you can eliminate some choices. But it seems to me that even a guess among four choices is +ev..
1/4 of the time you get it right and earn one point: 0.25 X 1 = +0.25
3/4 of the time you get it wrong and lose 1/4 point: 0.75 X -0.25 = -0.1875
add ev = 0.25 + -0.1875 = +0.0625
Compare this to your EV from leaving the question blank which is zero, and it looks to be like guessing is OK - of course the EV only increases if you CAN eliminate choices.
The other option is that I'm a dumbass and doing this all wrong. Which is it?
0
Guessing On A Multiple Choice Exam...
Started by Max_Powers, Aug 22 2008 08:02 PM
13 replies to this topic
#1
Max_Powers
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Posted 22 August 2008 - 08:02 PM
#2
jeff_536
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What?
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Posted 22 August 2008 - 08:08 PM
One guess in four you'll be right for 1 point
three guesses in four you'll be wrong for -.75.
+.25 points for every four guesses = .0625/guess.
looks right to me.
three guesses in four you'll be wrong for -.75.
+.25 points for every four guesses = .0625/guess.
looks right to me.
#3
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Posted 22 August 2008 - 08:10 PM
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#4
Actuary
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Posted 22 August 2008 - 08:36 PM
perhaps there are 5 answer choices on this exam?
#5
SuitedAces21
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Posted 22 August 2008 - 08:37 PM
QUOTE (Actuary @ Saturday, August 23rd, 2008, 12:36 AM) <{POST_SNAPBACK}>
perhaps there are 5 answer choices on this exam?
mind = blown.
#6
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Posted 22 August 2008 - 08:53 PM
pagin LLY!
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#7
Max_Powers
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Posted 23 August 2008 - 05:42 AM
QUOTE (Actuary @ Friday, August 22nd, 2008, 10:36 PM) <{POST_SNAPBACK}>
perhaps there are 5 answer choices on this exam?
Perhaps you can eliminate one choice?
But even with 5 choices its a break-even bet.
To look at it another way, if you randomly fill in 100 5 choice questions, are expected to get 20 correct for 20 points. The other 80 you lose 1/4 point each for -20. Overall, zero - the same as not answering any.
It seems to me you should always guess, because at worst its break even with five choices if you are making a totally random choice. However, usually you can eliminate one or more choices, or at least get a "feeling" about one choice that is better than the others, pushing the odds into your favor.
BTW the test I am speaking of is the high school AP exam (I'm a teacher) and several guides to the exam I've come across advise against guessing, or say only to guess if you can reduce the choices to 50/50. So I wonder if I'm missing something, but it doesn't look like it to me.
#8
Balloon guy
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Posted 23 August 2008 - 05:46 AM
Why are they making a wrong answer of less value than a right one?
Shouldn't a wrong one be -1 and a right one +1?
Stoopid schools
Shouldn't a wrong one be -1 and a right one +1?
Stoopid schools
I use my cigar smoke as idiot repellent
"The whole modern world has divided itself into Conservatives and Progressives. The business of Progressives is to go on making mistakes. The business of the Conservatives is to prevent the mistakes from being corrected." G.K. Chesterson 1900
"The whole modern world has divided itself into Conservatives and Progressives. The business of Progressives is to go on making mistakes. The business of the Conservatives is to prevent the mistakes from being corrected." G.K. Chesterson 1900
timwakefield, on 18 April 2012 - 10:38 AM, said:
Things are only rights because the government decides they should be rights.
#9
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Posted 23 August 2008 - 06:55 AM
The answer is obvious; you answer 0 questions and hand in a blank exam. This eliminates variance.
[15:06] <Jan99> go J E T S
#10
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Posted 23 August 2008 - 07:07 AM
lol at people who get answers wrong
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LOL. Dawson doesn't use condoms. He is immune to STD's and has impeccable control over his sperm as to only impregnate on command.
#11
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Posted 23 August 2008 - 08:10 AM
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#12
Actuary
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Posted 23 August 2008 - 04:01 PM
QUOTE (Max_Powers @ Saturday, August 23rd, 2008, 8:42 AM) <{POST_SNAPBACK}>
Perhaps you can eliminate one choice?
But even with 5 choices its a break-even bet.
But even with 5 choices its a break-even bet.
ok, I was making a guess as to why they used a 1/4 penalty.
The rationale for not guessing then, would be that you could spend more time on ones you know.
Obviously f you can reduce your choices, guessing is +EV
also, perhaps ansers are written by experts who know what to put that leads people to guess incorrectly.
Id have a pre planned guessing algorithm. Something that utilizes the fibonocci series works well.
#13
phlegm
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Posted 23 August 2008 - 05:25 PM
Any question u dont get right is wrong.
or am i missing something?
or am i missing something?
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#14
Actuary
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Posted 23 August 2008 - 05:27 PM
QUOTE (phlegm @ Saturday, August 23rd, 2008, 8:25 PM) <{POST_SNAPBACK}>
Any question u dont get right is wrong.
or am i missing something?
or am i missing something?
you seem to grasp it
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