Question 1119555
this looks like a binomial distribution type of problem.


p = .3 equals probability that a person has brown hair.
q = 1 - p = .7 equsls probability that a person doesn't have brown hair.


the formula is p(x) = c(n,x) * p^2 * q^(n-x)


in the first problem, n = 3 and you are looking for the probability that all 3 have brown hair.


formula becomes p(3) = .3^3 * .7^0 * c(3,3).


this is equal to .027 * 1 * 1 = .027


that would be selection b.


in the second problem, n = 2 and you are looking for the probability that at least 1 has brown hair.


that would be equal to 1 minus the probability that all 2 do not have brown hair.


formula becomes p(0) = .3^0 * .7^2 * c(2,0).


this is equal to 1 * .49* 1 = .49


that's the probability that none have brown hair.


the probability that at least 1 has brown hair would be 1 minus .49 = .51


that would be selection b.


the complete probabilities should always add up to 1.


those complete probabilities are shown in the following excel printout.


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