Question

A Retirement Confidence Survey of 1153 workers and retirees in the United States 25 years of age and older conducted by Employee Benefit Research Institute in January 2010 found that 496 had less than $10,000 in savings.

Obtain a point estimate for the population proportion of workers and retirees in the United States 25 years of age and older who have less than $10,000 in savings.

What is the upper bound for the 95% confidence interval?

What is the lower bound for the 95% confidence interval?

Answer 1

(1)

= Point Estimate = 496/1153 = 0.4302

(2)

n = Sample Size = 1153

SE =

= 0.05

From Table, critical values of Z = 1.96

Upper bound of Confidence Interval = 0.4302 + (1.96 X 0.0146) = 0.4302 + 0.0286 = 0.4588

Lower bound of Confidence Interval = 0.4302 - (1.96 X 0.0146) = 0.4302 - 0.0286 = 0.4016

So, Answers are:

Upper bound of Confidence Interval = 0.4588

Lower bound of Confidence Interval = 0.4016