Posted by **ryan** on Saturday, May 1, 2010 at 4:16pm.

You are taking a multiple choice test that has 20 questions with 4 possible answers each. You randoming quess each answer. What is the probality of getting 7 questions correct?

- Probability -
**bobpursley**, Saturday, May 1, 2010 at 4:28pm
Pr(7 right, 13 wrong)= .25^7 * .75^13 * number of ways

the number of ways is 20!/(7!13!)

((20 !) / ((7 !) * (13 !))) * (.25^7) * (.75^13) = 0.112406195

check my thinking.

- Probability -
**SraJMcGin**, Saturday, May 1, 2010 at 4:44pm
And here are some probability tutorials you might find handy:

http://search.yahoo.com/search?fr=mcafee&p=probability+tutorial

Sra

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