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 3 months. Here are comparative boxplots of the data:

a. Write a few sentences comparing the percent changes in BMC for the two groups. After checking that the conditions for inference are met, the researchers perform a test of  versus  Ha: μ_BF − μ_NP < 0, where  = the true mean percent change in BMC for breast-feeding women and  = the true mean percent change in BMC for women who are not pregnant or lactating. Computer output from the test is shown.

b. What conclusion should the researchers make at the  significancelevel?

c. Can we conclude that breast-feeding causes a mother’s bones to weaken? Why or why not?

d. Based on your conclusion in part (b), which type of error—a Type I error or a Type II error—could you have made? Explain your answer.

Transcribed Image Text:

Breast- feeding Not pregnant -10 -8 -6 -4 -2 0 2 4 Percent change in BMC Group