Question

A study of iron deficiency among infants compared samples of infants following different feeding regimens. One group (23 infants) contained breast-fed infants, while the infants in another group (19 infants) were fed a standard baby formula with no additional iron supplements. At 12 months of age, the hemoglobin levels of both groups were assessed. The mean hemoglobin level of the breast-fed group was 13.3, with a standard deviation of 1.7. The formula fed group had a mean level of 12.4, with a standard deviation of 1.8. (Units in g/Dl, normal range is around 11-13 for infants.)

Find the 95% Confidence interval.

Answer 1

Standard error of mean difference= sqrt(s1^2/n1+s2^2/n2)

SE= sqrt((1.7)^2/23+(1.8)^2/19)

SE= 0.544

degrees of freedom= 37

t critical value=2.03

Margin of error = tc *SE= 0.544*2.03= 1.104

95% confidence interval is

difference of means MOE

is 95% CI