SOLUTION: Suppose a quiz has 9 multiple choice questions. Each question has 4 answer choices. If a student takes the quiz and randomly guesses on every question Find the probability the stu

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Question 990166: Suppose a quiz has 9 multiple choice questions. Each question has 4 answer choices. If a student takes the quiz and randomly guesses on every question
Find the probability the student gets between 2 and 7, exclusive, questions correct
Find the probability the student gets more than 5 questions correct.
please help me out!
Thanks
Answer by solver91311(24713)   (Show Source): You can put this solution on YOUR website!


The probability of successes in trials where is the probability of success on any given trial is given by:



Where is the number of combinations of things taken at a time and is calculated by

For the first one, you need 3 of 9 plus 4 of 9 plus 5 of 9 plus 6 of 9 where p = 0.25.

More than 5 is 6, 7, 8, or 9.

Get out your calculator or if you have Excel:
=BINOMDIST(6,9,0.25,TRUE) - BINOMDIST(2,9,0.25,TRUE)

and

=1-BINOMDIST(5,9,0.25,TRUE)

By the way, these same formulas work in Numbers on a Mac

John

My calculator said it, I believe it, that settles it

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