Twin births. In 2000, the Journal of the American Medical Association (JAMA) published a study that examined pregnancies that resulted in the birth of twins. Births were classified as preterm with intervention (induced labor or cesarean), preterm without procedures, or term/postterm. Researchers also classified the pregnancies by the level of prenatal medical care the mother received (inadequate, adequate, or intensive). The data, from the years 1995-1997, are summarized in the table below. Figures are in thousands of births.

a) What percent of these mothers received inadequate medical care during their pregnancies?

b) What percent of all twin births were preterm?

c) Among the mothers who received inadequate medical care, what percent of the twin births were preterm?

d) Create an appropriate graph comparing the outcomes of these pregnancies by the level of medical care the mother received.

e) Write a few sentences describing the association between these two variables.