An obstetrician wants to learn whether the amount of prenatal care and the wante
ID: 2959392 • Letter: A
Question
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:Wantedness of Months Pregnant Before Prenatal Care Began
Pregnancy Less than 3 mos. 3 to 5 mos. More than 5 mos.
Intended 593 26 33
Unintended 64 8 11
Mistimed 169 19 16
a. Using a 5% level of significance, test the null hypothesis that the frequency of the wantedness of the pregnancy is independent of the when the prenatal care began.
b. Compute the chi-square test statistic.
Explanation / Answer
The test hypothesis is Ho: indepenedent Ha: not independent The test statistic is Chi-square = 21.357 degrees of freedom = 4 p-value = 0.00026901 Since the p-value is less than a=0.05, we reject Ho. So we can conclude that the frequency of the wantedness of the pregnancy is not independent of the when the prenatal care began.