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

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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**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,872

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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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 93,790

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

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

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