A random sample of n = 15 heat pumps of a certain type yielded the following observations on lifetime (in years): 2.0 1.1 6.0 1.6 5.3 0.4 1.0 5.3 15.6 0.8 4.8 0.9 12.2 5.3 0.6 (a) Assume that the lifetime distribution is exponential and use an argument parallel to that of this example to obtain a 95% CI for expected (true average) lifetime. (Round your answers to two decimal places.) years (b) How should the interval of part (a) be altered to achieve a confidence level of 99%? O A 99% confidence level requires using a new value of n to capture an area of 0.005 in each tail of the chi-squared distribution. O A 99% confidence level requires using a new value of n to capture an area of 0.1 in each tail of the chi-squared distribution. A 99% confidence level requires using critical values that capture an area of 0.005 in each tail of the chi-squared distribution. O A 99% confidence level requires using critical values that capture an area of 0.1 in each tail of the chi-squared distribution. (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?] (Round your answers to two decimal places.) years