Playbill magazine reported that the mean annual household incomeof its readers is $120,255. (Playbill, January 2006). Assume thisestimate of the mean annual household income is based on a sampleof 80 households, and based on past studies, the populationstandard deviation is known to be σ = $33,225.
a. Develop a 90% confidence interval estimate of the populationmean.
b. Develop a 95% confidence interval estimate of the populationmean.
c. Develop a 99% confidence interval estimate of the populationmean.
d. Discuss what happens to the width of the confidence intervalas the confidence level is increase. Does this result seemreasonable? Explain.
