The average yearly snowfall in a city is 55 inches, and yearly snowfalls are distributed normally.

• What is the standard deviation if 15 percent of the years have snowfalls above 60 inches?
• Based on this standard deviation, what is the probability that the average snowfall in the next 10 years will be greater than 56 inches?

Only 27 percent of college students believe that they manage time effectively. If you took a sample of 220 college students, what is the probability that more than 29 percent in your sample would say that they manage their time effectively?

In one hospital, 1000 babies are born during the summer. In another hospital, 500 babies are born. Assuming that there is a 50 percent probability that any baby born will be male, which hospital is more likely to have less than 47% male births?

Assume that life spans are normally distributed. The longevity of people in Nagano, Japan has a standard deviation of 14 years. What is the mean longevity if 30% of the people live longer than 75 years?

Assume that battery life is distributed normally with a mean of 218 hours and a standard deviation of 11 hours. How large a sample of batteries would you have to take to have a probability of 90 percent that the average battery life in the sample is between 216 and 220 hours?