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## #1 2012-10-01 12:44:24

Skyblast72
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### 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!

## #2 2012-10-01 16:47:11

bob bundy
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### Re: Probability of guessing questions on a test

hi Skyblast72,

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

Bob

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

## #3 2012-10-01 19:50:11

bobbym

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### 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 have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #4 2012-10-01 22:25:46

Skyblast72
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### Re: Probability of guessing questions on a test

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