An obstetrician wants to learn whether the amount of prenatal care and the wantedness of the pregnancy are associated. He randomly selects 939 women who had recently given birth and asks them to disclose whether their pregnancy was intended, unintended, or mistimed. In addition, they were to disclose when they started receiving prenatal care, if ever. The results of the survey are as follows:

(a) Compute the expected values of each cell under the assumption of independence.
(b) Verify that the requirements for performing a chi-square test of independence are satisfied.
(c) Compute the chi-square test statistic.
(d) Test whether prenatal care and the wantedness of pregnancy are independent at the a = 0.05 level of significance.
(e) Compare the observed frequencies with the expected frequencies. Which cell contributed most to the test statistic? Was the expected frequency greater than or less than the observed frequency? What does this information tell you?
(f) Construct a conditional distribution by wantedness of the pregnancy and draw a bar graph. Does this evidence support your conclusion in part (d)?

Transcribed Image Text:

Months Pregnant before Prenatal Care Began Wantedness of Pregnancy 3 to 5 Months Less Than More Than 5 Months (or never) 3 Months 33 593 26 Intended Unintended 64 11 19 Mistimed 169 16