6. Each member of a random sample of 15 business economists was asked to

predict the rate of in‡ation for the coming year. Assume that the predictions

for the whole population of business economists follow a normal distribution

with standard deviation 1.8%.

a. The probability is 0.01 that the sample standard deviation is bigger than

what number?

b. The probability is 0.025 that the sample standard deviation is smaller

than what number?

c. Find any pair of numbers such that the probability that the sample stan-

dard deviation lies between these numbers is 0.90.

I am not sure how to do this. I feel like I am missing a piece of information but I am not.