Repeat Exercise 20 for samples of size 30 and 45. What happens to the mean and the standard deviation of the distribution of sample means as the size of the sample increases?

Exercise 20

The braking distances (from 60 miles per hour to a complete stop on dry pavement) of a car are normally distributed, with a mean of 136 feet and a standard deviation of 4.66 feet. Random samples of size 15 are drawn from this population, and the mean of each sample is determined.

Use the Central Limit Theorem to find the mean and standard deviation of the indicated sampling distribution of sample means. Then sketch a graph of the sampling distribution.