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(Tree diagram). In survey of 290 self-selected respondents, 211 said they would

ID: 3366157 • Letter: #

Question

(Tree diagram). In survey of 290 self-selected respondents, 211 said they would not trust a public defender to represent them if they needed a lawyer. Assume that the remaining respondents said that they would trust a public defender. Further assume that this result is true for the current population of the adults. Two adults are selected at random and asked whether or not they would trust a public defender to represent them if they needed a lawyer. Draw a tree diagram for this problem. Find the probability that in this sample of two adults 3. a. neither one would trust a public defender, b. at most one would trust a public defender.

Explanation / Answer

p = 211/290 = 0.73

n = 2

It is a binomial distribution.

P(X = x) = nCx * px * (1 - p)n - x

a) P(X = 0) = 2C0 * (0.73)^0 * (1 - 0.73)^2

                   = 0.0729

b) P(X < 1) = P(X = 0) + P(X = 1)

                   = 2C0 * (0.73)^0 * (1 - 0.73)^2 + 2C1 * (0.73)^1 * (1 - 0.73)^1

                   = 0.4671