SOLUTION: a true/ flase quiz has 10 questions. If a student randomly guesses on each question, qhat is the probability of getting at least 3 correct?
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Question 807476: a true/ flase quiz has 10 questions. If a student randomly guesses on each question, qhat is the probability of getting at least 3 correct?
Answer by solver91311(24713) (Show Source): You can put this solution on YOUR website!
What do "flase" and "qhat" mean? Which is to say, please have the common courtesy to check your post for obvious spelling and other errors BEFORE you push the send button.
In the meantime:
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 !})
"At least 3" means the probability of exactly 3 plus exactly 4, plus exactly 5, ... and so on. A much simpler calculation that gets you to the same place is 1 minus the probabilities of exactly zero, plus exactly 1, plus exactly 2. So:
\ =\ 1\ -\ \sum_{k=0}^2\,{{10}\choose{k}}\left(0.5\right)^k\left(0.5\right)^{10\,-\,k})
Happy calculating.
John
Egw to Beta kai to Sigma
My calculator said it, I believe it, that settles it
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