Question: Does breast-feeding weaken bones? Breast-feeding mothers secrete calcium into their milk. Some of the calcium may come from their bones, so mothers may lose bone mineral. Researchers compared a random sample of 47 breast-feeding women with a random sample of 22 women of similar age who were neither pregnant nor lactating. They measured the percent change in the bone mineral content (BMC) of the women's spines over three months. Comparative boxplots and summary statistics for the data from Fathom are shown below.
(a) Based on the graph and numerical summaries, write a few sentences comparing the percent changes in BMC for the two groups.
(b) Is the mean change in BMC significantly lower for the mothers who are breast-feeding? Give appropriate evidence to justify your answer.
(c) Can we conclude that breast-feeding causes a mother's bones to weaken? Why or why not?