4. From a random sample of 21 teenagers living in Columbus, OH, a 99% confidence interval for the mean distance (in miles) between home and the nearest public park larger than 20 acres for all teens living in Columbus, OH is: 3.6 < < 9.1

a) Find the sample mean.

b) Find the margin of error of the confidence interval.

c) Find the critical value used to create the confidence interval.

d) If a 90% confidence interval had been made, using the same data, would this interval be narrower, wider, or the same as the given interval?

e) Explain the meaning of the given confidence interval in context.