In the 1980s, it was generally believed that congenital abnormalities affected about 5 % of the nation’s children. Some people believe that the increase in the number of chemicals in the environment has led to an increase in the incidence of abnormalities. A recent study examined 384 children and found that 46 of them showed signs of an abnormality. Is this strong evidence that the risk has increased? (We consider a P-value of around 5% to represent reasonable evidence.)

a) Write appropriate hypotheses.

b) Check the necessary assumptions.

c) Perform the mechanics of the test. What is the P-value?

d) Explain carefully what the P-value means in this context.

e) What’s your conclusion?

f) Do chemicals in the environment cause congenital abnormalities?