<PRE><B>Question 285518</B>
suppose you are writing a multiple choice exam in which each answer has 5 choices. you decide to use in which you place 5 balls in a box (marked A,B,C,D,E). you randomly select 1 ball for each question and replace it, the marking on the ball determines your answer to the question. If there are 10 questions,
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Binomial Problem with n = 10 ; p = 1/5 
1. what is the probability of getting 5 questions correct?: 
Ans: binompdf(10,1/5,5) =
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2. getting at least 3 questions correct?:
Ans: 1-binomcdf(10,1/5,2) = 
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3. what is the expected number of correct answers?
ans: mean = np = 10(1/5) = 2
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4. what is the standard deviation?
 Ans: std = sqrt(npq) = sqrt(2*4/5) = sqrt(8/5) = 1.2649

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Cheers,
Stan H.
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