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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.
90% of mathematicians do not understand 90% of currently published mathematics.
I am willing to wager that over 75% of the new words that appeared were nothing more than spelling errors that caught on.

#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.