Question

Seventeen percent of U.S. residents are in their thirties. Consider a group of nine U.S. residents selected at random. Find the probability that three or four of the people in the group are in their thirties.

Answer 1

0.1764

Explanation:

This problem meets requirement that enables us to use the binomial probability relation :

Probability of success, p = 17% = 0.17

number of trials = 9

(1 - p) = 1 - 0.17 = 0.83

The binomial probability relation :

P(x = x) = nCx * p^x * (1 - p)^(n-x)

P(x = 3) = 9C3 * 0.17^3 * 0.83^6

P(x = 3) = 84 * 0.001606258054361897

P(x = 3) = 0.134925676566399348

P(x = 3) = 0.13492

P(x = 4) = 9C4 * 0.17^4 * 0.83^5

P(x = 4) = 126 * 0.000328992613544003

P(x = 4) = 0.041453069306544378

P(x = 4) = 0.04145

P(x = 3 or x = 4) = P(x = 3) + p(x = 4)

= 0.13492 + 0.04145

= 0.17637

= 0.1764