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:
\ =\ {{n}\choose{k}}\left(p\right)^k\left(1\,-\,p\right)^{n\,-\,k})
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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