Assignment:
Playbill magazine reported that the mean annual household income of its readers is $119.155 (Playbill, January 2006). Assume this estimate of the mean annual household income is based on a sample of 80 households and based on past studies, the population standard deviation is known to be σ = $30,000.
a. Develop a 90% confidence interval estimate of the population mean.
b. Develop a 95% confidence interval estimate of the population mean.
c. Develop a 99% confidence interval estimate of the population mean.
d. Discuss what happens to the width of the confidence interval as the confidence as the confidence level is increased. Does this seem reasonable? Explain.
Provide complete and step by step solution for the question and show calculations and use formulas.