Challenging Economics math Equation.?

Question

An economics professor randomly selected 100 millionaires in the U.S. The average age of these millionaires was 52.1 years with a standard deviation of 12.3 years. What is a 99.5% confidence interval for the mean age, m, of all U.S. millionaires?



a. 48.6 < m < 55.6

b. 48.9 < m < 55.3

c. 49.2 < m < 55.0

d. 49.7 < m < 54.5

e. 50.1 < m < 54.1

f. none of these

Answer 1

[52.1 - 2.575*12.3/sqrt(100) , 52.1 + 2.575*12.3/sqrt(100)]

= [48.93275, 55.26725]

= [48.9, 55.3] (b.)

Answer 2

use t test and then go on with your life.