Student study times. A class survey in a large class for first-year college stud
ID: 3290130 • Letter: S
Question
Student study times. A class survey in a large class for first-year college students asked, "About how many minutes do you study on a typical weeknight?" The mean response of the 463 students was x = 118 minutes. Suppose that we know that the study time follows a Normal distribution with standard deviation sigma = 65 minutes in the population of all first-year students at this university. (a) Use the survey result to give a 99% confidence interval for the mean study time of all first -year students. (b) What condition not yet mentioned must be met for your confidence interval to be valid?Explanation / Answer
Solution:
Given n = 463, x = 118 , = 65
a. Given = 0.01, |Z(0.005)| = 2.58 (check standard normal table)
So 99% CI is
xbar± Z*s/n
--> 118 ± 2.58*65/sqrt(463)
--> (110.20632, 125.79368)
b. whether the sample is representative, since it covers just one class.