The math department wants to order class calculators for all their teachers. It is a lot of money to spend, so they
want to make sure they are getting the best calculators out there. They select an SRS of 50 calculators from
Company A and find that 3 of them do not work correctly. The select an SRS of 60 calculators from Company
B and find that 5 calculators do not work correctly.
18) Which of the following represents a 90% confidence interval for a difference in proportions PA-
PB, where PÅ is the proportion of Company A's calculators that are defective, and pв is the proportion of
Company B's calculators that are defective?
(A)-0.02 ± 1.96
(B)-0.02 ± 1.96
(C) -0.02 + 1.64
D-0.02 +1.64
(E)-0.02 +1.64
(0.06) (0.94)
50
(0.06) (0.94)
50
(0.06) (0.94)
50
(0.06) (0.94)
50
+
+
(0.073)(0.927)
110
(0.08) (0.92)
60
(0.08) (0.92)
60
(0.08) (0.92)
60
(0.08) (0.92)
60