A study of iron deficiency among infants compared samples ofinfants following different feeding regimens. One group containedbreast-fed infants, while the infants in another group were fed astandard baby formula without any iron supplements. Here aresummary results on blood hemoglobin levels at 12 months of age.

Group n x s

Breast-fed 22 13.3 1.7

Formula 18 12.4 1.8

(a) Is there significant evidence that the mean hemoglobin levelis higher among breast-fed babies? State H0 and Ha.

H0: μbreast-fed = μformula; Ha: μbreast-fed > μformula

H0: μbreast-fed < μformula; Ha: μbreast-fed = μformula

H0: μbreast-fed > μformula; Ha: μbreast-fed = μformula

H0: μbreast-fed ≠ μformula; Ha: μbreast-fed < μformula

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

t =

P-value =

What is your conclusion?

Reject the null hypothesis. There is significant evidence thatthe mean hemoglobin level is higher among breast-fed babies.

Reject the null hypothesis. There is not significant evidencethat the mean hemoglobin level is higher among breast-fedbabies.

Fail to reject the null hypothesis. There is significantevidence that the mean hemoglobin level is higher among breast-fedbabies.

Fail to reject the null hypothesis. There is not significantevidence that the mean hemoglobin level is higher among breast-fedbabies.

(b) Give a 95% confidence interval for the mean difference inhemoglobin level between the two populations of infants. (Roundyour answers to three decimal places.) ,

(c) State the assumptions that your procedures in (a) and (b)require in order to be valid.

We need sample sizes greater than 40.

We need the data to be from a skewed distribution.

We need two independent SRSs from normal populations.

We need two dependent SRSs from normal populations.