SOLUTION: Rafael is taking a test that contains a section of 12 true-false questions. How many of the possible groups of answers to these questions have exactly 8 correct answers of false?

Question 812842: Rafael is taking a test that contains a section of 12 true-false questions. How many of the possible groups of answers to these questions have exactly 8 correct answers of false?

Answer by ewatrrr(24785) (Show Source): You can put this solution on YOUR website!

 

Hi,

12 true-false questions.

Note: The probability of x successes in n trials is: 

P = nCx*  where p and q are the probabilities of success and failure respectively. 

In this case p & q are = 1/2 or .5

nCx = 

P(8 false answers) = 12!/8!4! (.5)^8(.5)^4 = 495(.5)^8(.5)^4 = .1208 

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