I need help with only Question 6.25

6.24 Total sleep time of college students. In Example 5.4 (page 293), the total sleep time per night among col- lege students was approximately Normally distributed with mean = 6.78 hours and standard deviation o-1.24 hours. You initially plan to take an SRS of size n = 175 and compute the average total sleep time. What is the standard deviation for the average time in hours? in minutes? Use the 95 part of the 68-95-99.7 rule to describe the variability of this sample mean. What is the probability that your average will be below 6.9 hours? 6.25 Determining sample size. Refer to the previous exercise. You really want to use a sample size such that about 95% of the averages fall within 15 minutes of the true mean = 6.78. Based on your answer to part (b) in Exercise 6.24, should the sample size be larger or smaller than 175? Ex- plain. What standard deviation of x do you need such that 95% of all samples will have a mean within 5 minutes of ? Using the standard deviation you calculated in part (b), determine the number of students you need to sam- ple