A random sample of heat pumps of n = 15a certain type yielded the following observation...

A random sample of heat pumps of n = 15a certain type yielded the following observations on lifetime (in years):

a. Assume that the lifetime distribution is exponential and use an argument parallel to that of Example 7.5 to obtain a 95% CI for expected (true average) lifetime.

b. How should the interval of part (a) be altered to achieve a confidence level of 99%?

c. What is a 95% CI for the standard deviation of the lifetime distribution? [Hint: What is the standard deviation of an exponential random variable?]