Refer to Exercise 9.

Compute the value of the test statistic.

Exercise 9

Two suppliers of machine parts delivered large shipments. A simple random sample of 150 parts was chosen from each shipment.

For supplier A, 12 of the 150 parts were defective. For supplier B, 28 of the 150 parts were defective. The question of interest is whether the proportion of defective parts is greater for supplier B than for supplier A. Let p1 be the population proportion of defective parts for supplier A, and let p2 be the population proportion of defective parts for supplier B. State appropriate null and alternate hypotheses.