A manufacturer receives parts from two suppliers. A simple random sample of 400 parts from Supplier 1 finds 20 defective. A simple random sample of 200 parts from Supplier 2 finds 20 defective. Let p 1 and p 2 be the proportion of all parts from Supplier 1 and Supplier 2, respectively, that are defective. Is the difference statistically significant at the 5% significance level? To determine this, test the hypotheses H 0: p 1 = p 2 versus H a: p 1 p 2.