In a recent survey, the total sleep time per night among college students was approximately normally distributed with mean μ = 6.78 hours and standard deviation σ = 1.24 hours. you plan to take an srs of size n = 150 and compute the average total sleep time. now you want to use a sample size such that about 95% of the averages fall within ±8 minutes (0.1333 hours) of the true mean μ = 6.78 (a) based on the fact that for n = 150, 2σx = 0.202, should the sample size be larger or smaller than 150? explain. the sample size should be larger than 150, because we are looking for a smaller standard deviation. the sample size should be smaller than 150, because we are looking for a larger standard deviation.

the sample size should be smaller than 150, because we are looking for a smaller standard deviation. correct: your answer is correct.

(b) using the 95 part of the 68−95−99.7 rule, what standard deviation of x do you need such that 95% of all samples will have a mean within 6 minutes of μ? (round your answer to four decimal places.)

0.05 correct: your answer is correct.

(c) using the standard deviation you calculated in part (b), determine the number of students you need to sample. (round your answer up to the nearest student.)

615 incorrect: your answer is incorrect.

students i don't understand how to calculate the population, part c. the others i chose the correct answers.