for mathematics was found to be 160 points. What is the probability that a random sample of 256 students will have a mean score of more than 623 ? Less than 604 ? The probability that a random sample of 256 students will have a mean score of more than 623 is 0.1841. (Round to four decimal places as needed.) The probability that a random sample of 256 students will have a mean score of less than 604 is (Round to four decimal places as needed.) A survey of 23 college freshmen found that they average 7.38 hours of sleep each night. A 90% confidence interval had a margin of error of 0.493. a. What are the lower and upper limits of the confidence interval? b. What was the standard deviation, assuming that the population standard deviation is known? a. The lower limit of the confidence interval is and the upper limit of the confidence interval is (Round to three decimal places as needed.)