In a city 20 of the population is under 25 years of age Thre

In a city, 20% of the population is under 25 years of age. Three people are selected at random from the city. Selecting one person is a trial. Let success correspond to selecting a person that is under 25 years of age.

Find the mean and standard deviation for the binomial distribution.

Solution

Given:
n = 3
p = .20
1-p = 1-.20 = .80

For a binomial random variable...

mean
= mu
= n x p
= 3(.20)
= .6

Answer: .6

standard deviation
= sigma
= sqrt(n x p x (1-p)) = sqrt(
= sqrt(3 x .20 x .80)
= .693

Answer: .693

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