In: Statistics and Probability
In 2009 the percentage of the U.S. population who was foreign-born was 12.2. Choose 60 U.S. residents at random. How many would you expect to be American-born? Find the mean, variance, and standard deviation for the number who are foreign-born.
Compute the number of American-born.
The percentage of the foreign-born is 12.2% and the percentage of the Americans is 87.8% (=100%–12.2%).
The American-born is,
= 52.68
≈ 53
Thus, approximately 53 are expected to be American-born.
Obtain the mean, variance, and standard deviation for the binomial distribution when n = 60, and p = 0.122.
Mean:
µ = np
= 60(0.122)
= 7.3
Variance:
σ2 = npq
= 60(0.122)(1 – 0.122)
= 60(0.122)(0.878)
= 6.4
Standard deviation:
σ = √npq
= √6.4
= 2.5
Mean = 7.3
Variance = 6.4
Standard deviation = 2.5