Two machines used in the same operation are to be compared. A random sample of 80 parts from the first machine yields 6 nonconforming ones. A random sample of 120 parts from the second machine shows 14 nonconforming ones.
a) Can we conclude that there is a difference in the output of the machines? Use a level of significance of 0.01.
b) Find a 95% confidence interval for the difference in the proportion of nonconforming parts between the two machines.