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#1 2012-09-30 14:44:24

Skyblast72
Member
Registered: 2012-09-30
Posts: 16

Probability of guessing questions on a test

Probability question:

A student takes a 19-question, multiple choice exam with three choices for each question and guesses on each question.  Find the probability of guessing exactly 8 out of 19 correctly.

I used 19C8  so n=19 x =8 p=.33 and q=.67 but I can't come up with any of the answers that are on my homework. 

I am a beginning statistics/probability student.  Showing your work would be helpful to me so I can learn how to do this stuff.  Thanks for any help you are able to give, I appreciate it!

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#2 2012-09-30 18:47:11

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,532

Re: Probability of guessing questions on a test

hi Skyblast72,

That seems to be the right method to me.  I made that 0.133182...

How about you?

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#3 2012-09-30 21:50:11

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,638

Re: Probability of guessing questions on a test

Hi;

With n = 8 and p = 1 / 3 and trials = 19.


In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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#4 2012-10-01 00:25:46

Skyblast72
Member
Registered: 2012-09-30
Posts: 16

Re: Probability of guessing questions on a test

THANK YOU!! I see where I messed up now.

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