Chapter 15, Problem 50E

Rainfall Statistics from Cornell’s Northeast Regional Climate Center indicate that Ithaca, New York, gets an average of 35.4" of rain each year, with a standard deviation of 4.2". Assume that a Normal model applies.

1. a) During what percentage of years does Ithaca get more than 40" of rain?
2. b) Less than how much rain falls in the driest 20% of all years?
3. c) A Cornell University student is in Ithaca for 4 years. Let $\bar{y}$ represent the mean amount of rain for those 4 years. Describe the sampling distribution model of this sample mean, $\bar{y}$.
4. d) What’s the probability that those 4 years average less than 30" of rain?