In a study of iron deficiency among infants, random samples of infants following different feeding programs were compared. One group contained breast-fed infants, while the children in another group were fed by a standard baby formula without any iron supplements. Here are summary results of blood hemoglobin levels at 12 months of age.
Group Sample Size Sample Mean Sample Std. Deviation
Breast-fed 8 13.3 1.7
Formula-fed 10 12.4 1.8
A 98% confidence interval for the mean difference in hemoglobin level between the two populations of infants is:
(-1.24, 3.04)
(-1.05, 3.75)
(-1.27, 3.07)
(-1.58, 3.38)
(1.25, 3.05)