SOLUTION: a true false test has 5 questions what is the probability of getting atleast 4 right by guessing all the answers
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Question 667012: a true false test has 5 questions what is the probability of getting atleast 4 right by guessing all the answers
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 !})
You want the probability of getting either 4 or 5, so calculate the probability of getting all 5 right:
\ =\ {{5}\choose{5}}\left(0.5\right)^5\left(1\,-\ 0.5\right)^{5\,-\,5})
then calculate the probability of getting exactly 4 right:
\ =\ {{5}\choose{4}}\left(0.5\right)^4\left(1\,-\ 0.5\right)^{5\,-\,4})
And then add the two values. Note: 
, 
, anything to the zero power is 1, and anything to the 1 power is itself.
John
My calculator said it, I believe it, that settles it
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