Suppose a business researcher wants to estimate the average travel time to work in Etobicoke using a 98% level of confidence. A random sample 211 Toronto commuters is taken and the travel time to work is obtained from each. The sample mean is 55.0 minutes, and the population standard deviation is estimated to be about 16.4 minutes. Compute a 98% confidence interval on the data. (Use the z-distribution.)

Round thez-value to 3 decimal places and the confidence interval values to 1 decimal place.For part (a), use a positivez-value.

(a) What is the criticalz-value that will need to be used to calculate the confidence interval?

(b) What is the 98% confidence interval? ?<< ?

In a time-use study, 24 randomly selected managers were found to spend a mean of 3.11 h each day on paperwork. The population standard deviation is known to be about 1.50 h. Construct the 95 % confidence interval for the mean time spent on paperwork by all managers.

Round thez-value to 3 decimal places and the confidence interval values to 2 decimal places.For part (a), use a positivez-value.

(a) What is the criticalz-value that will need to be used to calculate the confidence interval?

(b) What is the 95% confidence interval? ?<