Statistics
posted by Kate .
A student group claims that firstyear students at a university must study 2.5 hours (150 minutes) per night during the school week. A skeptic suspects that they study less than that on the average. A class survey finds that the average study time claimed by 269 students is = 144 minutes, with a sample standard deviation of 70.
A) Regard these students as a random sample of all firstyear students and suppose we know that the study times follow a Normal distribution. What is the standard error of the sample mean?
B) Consider the hypotheses H0: μ = 150 against Ha: μ < 150. What is the value of the test statistic? Give your answer to two decimal places.

Z = (144150/Standard Error (SE) of the mean
SE = SD/sq rt of n1
I hope this helps.