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	23	13.3	1.7
Formula	18	12.6	1.8

(a)

Is there significant evidence that the mean hemoglobin level ishigher among breast-fed babies? State H₀ andH_a.H₀:

____H₀:?_breast-fed >?_formula;   H_a:?_breast-fed = ?_formula

_{_____H0}: ?_breast-fed formula;   H_a:?_breast-fed =?_formula  

____H₀: ?_breast-fed ??_formula;   H_a:?_breast-fed < ?_formula

____H₀: ?_breast-fed =?_formula;   H_a:?_breast-fed > ?_formula

Carry out a t test. Give the P-value. (Use? = 0.01. Use ?_breast-fed ??_formula. Round your value for t tothree decimal places, and round your P-value to fourdecimal places.)

t	=
P-value	=

What is your conclusion?

____Reject the null hypothesis. There is significant evidencethat the mean hemoglobin level is higher among breast-fedbabies.

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

____ Fail to reject the null hypothesis. There is notsignificant evidence that the mean hemoglobin level is higher amongbreast-fed babies.

____Fail to reject the null hypothesis. There is 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.)

________, _________ Answers

__C)

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

____We need two dependent SRSs from normalpopulations.

____We need sample sizes greater than40.  

____ We need two independent SRSs from normalpopulations.

_____We need the data to be from a skeweddistribution.