Using a 90% confidence level, the U. S. Department of Labor would like to estimate the average weekly hours worked by private employees in the United States who are adults. Assume the standard deviation for the number of hours worked is seven hours. Determine the sample sizes needed to construct this confidence interval using the following margins of error:
a. 2 hours
b. 1 hour
c. 30 minutes
d. Explain why the margin of error affects the sample size needed to obtain a particular confidence level.