Question 1038156: Suppose that there are 100 students in your business statistics class, of whom 10 are left-handed. Twenty students are selected at random. What is the probability that at least 80% of the students are right-handed?
So far I tried to put it in my calculator as
P = 0.8
X = 16 (since 80% of 20 is 16)
N = 20
in binomial distribution but it hasn't worked
The answer is 0.9568
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! The probability of being right handed is 90%, not 80%.
Use the binomial table n=20, p=0.9,
You count the ones above 15, and the probability (cumulative) that 15 are right handed is 0.0432. From 16 to 20 is the remaining probability, and that is 0.9568.
You can use 20C16(0.9)^16(0.1)^4, but you also have to do 17,18,19, and 20, since the question asks "at least" 80%.
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