Question

In a study of life expectancy in Boston, a random sample of 19 people lived an average of 74.2 years. Suppose the population standard deviation is σ = 10.2 years, Find a 90% confidence interval for the mean of life expectancy in Boston.

Answer 1

Solution :

Given that,

Sample size = n = 19

Z/2 = 1.645

Margin of error = E = Z/2* ( /n)

= 1.645 * (10.2 / 19)

Margin of error = E = 3.8

At 90% confidence interval estimate of the population mean is,

- E < < + E

74.2 - 3.8 < < 74.2 + 3.8

70.4 < < 78

(70.4 , 78)