Let X1, ..., Xn be a random sample from a two-parameter exponential distribution, Xi ~ EXP (theta, eta).
a) Assuming it is known that eta = 150, find a pivotal quantity for the parameter theta based on the sufficient statistic.
b) The following data are mileages for 19 military personnel carriers that failed in service: 162, 200, 271, 320, 393, 508, 539, 629, 706, 777, 884, 1008, 1101, 1182, 1463, 1603, 1984, 2355, 2880. Find a one-sided lower 95% confidence limit for theta.