Question

A study of iron deficiency among infants compared samples of infants following different feeding regimens. One group contained breast-fed infants, while the infants in another group were fed a standard baby formula without any iron supplements. Here are summary results on blood hemoglobin levels at 12 months of age.

Group	n	x	s
Breast-fed	22	13.1	1.5
Formula	20	12.4	1.6

(a)

Is there significant evidence that the mean hemoglobin level is higher among breast-fed babies? State H₀ and H_a.

H₀: μ_breast-fed > μ_formula;   H_a: μ_breast-fed = μ_formulaH₀: μ_breast-fed ≠ μ_formula;   H_a: μ_breast-fed < μ_formula    H₀: μ_breast-fed = μ_formula;   H_a: μ_breast-fed > μ_formulaH₀: μ_breast-fed < μ_formula;   H_a: μ_breast-fed = μ_formula

Carry out a t test. Give the P-value. (Use α = 0.01. Use μ_breast-fed − μ_formula. Round your value for t to three decimal places, and round your P-value to four decimal places.)

t	=
P-value	=

(b)

Give a 95% confidence interval for the mean difference in hemoglobin level between the two populations of infants. (Round your answers to three decimal places.)

( , )

Answer 1