SOLUTION: determine the probability of randomly guessing 40 questions correct out of 60 questions on a multiple choice test with possible selections a,b,c,d,e; by guessing
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Question 271712: determine the probability of randomly guessing 40 questions correct out of 60 questions on a multiple choice test with possible selections a,b,c,d,e; by guessing
Answer by solver91311(24713) (Show Source): You can put this solution on YOUR website!
The probability of exactly 
successes in 
trials where the probability of success on any given trial is 
is given by:
\ =\ \left(n\cr k\right)p^k\left(1\,-\,p\right)^{n-k})
Where )
is the number of ways to select things from a collection of things and is equal to !})
Since there are 5 responses to each question, the probability of a random correct response on any given question is 
.
Just plug in the numbers...
\ =\ \left(60\cr 40\right)\left(0.2\right)^{40}\left(0.8\right)^{20})
And do the arithmetic.
John
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