Question

A study of iron deficiency in infants compared samples of infants whose mothers chose different ways of feeding them. One group contained breast-fed infants. The children in another group were fed a standard baby formula without any iron supplements. Her are summary results on blood hemoglobin levels at 12 months of age:

Group	n	mean x	s
Breast-fed	25	15.4	2.2
Formula	32	17.1	1.9

Part a: We want to see if the mean hemoglobin level is greater among formula-fed babies. State the hypotheses and

part b perform the significance test on your hypothesis. Report the test statistic and p-value. State your conclusion in terms of the issue.

Part c: Give a 95% confidence interval for the mean difference in hemoglobin level between the two populations of infants.

Answer 1

Let denote the mean hemoglobin level among breast-fed babies and formula-fed babies.