A suvey of 23 college freshmen foind that they average 7.49 hoirs of sloep each night. A 90% corfidence intervai had a magin of emor of 0.492. a. What are the lower and upper imits of the conficence intenal? b. What was the standard devision, assumng that the populalion sanderd deviation is known? a. The iskec limit of the combidanos intervai is and the upper imit of the osefisence interval is (fiound to thee decimal pleces as needed.)