In semiconductor manufacturing process, three wafers from a lot are tested. Each wafer is classified as pass or fail. Assume the probability that a wafer passes the test is 0.8 and that wafers are independent.
a) Determine the probability mass function of the number of wafers from a lot that passes the test.
b) Determine the cumulative distribution for the number of wafers that pass the test.
c) What is the mean number of wafers you expect to pass the test?
d) What is the variance of the number of wafers you expect to pass the test?