A. The table below shows the results of a survey in which 400 adults from the East, 400 adults from the South, 400adults from the Midwest, and 400 adults from the West were asked if traffic congestion is a serious problem.

Adults who say that traffic congestion is a serious problem

Region Percentage

East 35%

South 32%

Midwest 26%

West 53%

Construct a 99% confidence interval for the proportion of adults from the Midwest who say traffic congestion is a serious problem. Is it possible that these two proportions are equal? Explain your reasoning.

The 99% confidence interval for the proportion of adults from the Midwest who say traffic congestion is a serious problem is ( ____ , _____ )

(Round to three decimal places as needed.)

B. In a random sample of 25 people, the mean commute time to work was 30.8 minutes and the standard deviation was 7.2 minutes. Assume the population is normally distributed and use a t-distribution to construct a 80% confidence interval for the population mean . What is the margin of error of ?

The margin of error of is ____ .

(Round to one decimal place as needed.)