Because of the multitude of positive health benefits for infants and mothers, one provision of the Affordable Care Act, commonly known as Obamacare, requires that insurance plans pay for
breast-feeding support for mothers, such as consultations and breast pumps. According to the Centers for Disease Control and Prevention, 55.3% of mothers were breast-feeding their six-month-old babies in 2016. Suppose Humana Health Insurance would like to estimate the proportion of mothers who breast-fed their children at six months in 2018. A random sample of 210 mothers with six-month-old babies was selected, 119 of which were breast-feeding.

a. Construct a 95% confidence interval to estimate the actual proportion of mothers with six-month-old babies that were breast-feeding in 2018.

b. What is the margin of error for this sample?

c. Is there evidence that this proportion has changed since 2016 based on this sample?