Question: The research department at the home office of New Hampshire conducts ongoing research on the causes of automobile accidents, the characteristics of the drivers and so on. A random sample of 400 policies written on a single person revealed 120 had at least one accident in the previous three-year period. Similarly, a sample of 600 policies written on married persons revealed that 150 had been in at least one accident. Use the .05 significance level.

a. Is there a significant difference in the proportions of single and married persons having an accident during a three-year period?

b. How certain are you?