Question

A survey of entry level corporate analysts in New York City asked, approximately how many hours per week do you work?

(a) If the population standard deviation is known to be 4.7 hours, and a random sample of 35 corporations yielded a mean of 50.5 hours, then construct a 90% confidence interval for the mean number of hours worked by entry level analysts.

(b) In the above confidence interval, suppose that we want a margin of error of +/- 1 hour. What sample size is needed to achieve this?

(c) As mentioned in class, it is unlikely that the population standard deviation is known. Suppose instead that the sample standard deviation was 4.7 hours. Using the other values from part (a), form a 90% confidence interval for the mean number of hours worked by entry level analysts.

Answer 1

Solution:

(a) The 90% confidence interval is:

b)

  

(c) The 90% confidence interval is: