Question

Suppose that of 400 people polled 225 of them say they plan retire by age 65. Find a (two-sided) 97% confidence
interval for number of people who plan to retire by age 65.

SHOW WORK

A. [.505, .620] B. [.509, .616] C. [.514, .611] D. [.516, .609

Answer 1

225 out of 400 people saidthat they plan to retire by 65.

The sample proportion , = 225/400

= 0.5625

z value for 97% confidence interval = 2.17

The confidence interval is = z * (1-)/n

= 0.5625 0.054

= (0.509 , 0.616)

Ans) B. [.509, .616]