Question 967190: What is the probability that in a sample of 10 drivers exactly 4 will have a medical aid
Answer by Theo(13342)   (Show Source):
You can put this solution on YOUR website! you don't have enough information to determine this.
if this is a binomial probability type problem, what you need is the proportion of the population of drivers that has a medical aid in general.
assuming that proportion is 20% of the population of drivers, then you would get the following:
p = .2
q = 1 - p = .8
n = 10
x = 4
the general formula is p(x) = c(n,x) * p^x * q^(n-x)
in your probolem, the formula would become p(4) = c(10,4) * .2^4 * .8^6 which would then become p(4) = 210 * .2^4 * .8^6 which becomes p(4) = .088080384.
if that proportion were 40%, then the formula would become p(4) = 10c4 * .4^4 * .6^6 which would then become p(4) = .250822656.
c(10,4) is the combination formula for how many sets of 4 can you get out of 10 things where order is not important.
c(10,4) = 10! / (4! * 6!) which is equal to 210.
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