M 362K, Spring 03, Smith
Assignment for Wednesday, November 19
To Hand In:
1. p. 291 #15.
2. p. 292 #22. Be sure to give your reasons. In part (b), be sure to specify
where the marginal density is zero.
3. The number if years a brand A battery lasts is an exponential random
variable X with parameter 1. The number of years that a brand B battery lasts
is an exponential random variable Y with parameter 2. X and Y are independent
a. Find the joint pdf of X and Y.
b. Find the probability that a randomly chosen brand A
battery lasts longer than a randomly chosen brand B battery.