Consider writing onto a computer disk and then sending it through a certifier that counts the number of missing pulses. Suppose this number X has a Poisson distribution with parameter . (Suggested in "Average Sample Number for Semi-Curtailed Sampling Using the Poisson Distribu- tion," J. Quality Technology, 1983: 126–129.)

a. What is the probability that a disk has exactly one missing pulse?

b. What is the probability that a disk has at least two missing pulses?

c. If two disks are independently selected, what is the probability that neither contains a missing pulse?