## Answers

**Given:**

sample size (n) | Mean () | SD (S) | |

Breast-fed | 22 | 13.3 | 1.6 |

formula | 20 | 12.7 | 1.7 |

a)

**ANSWER: C.**

**H0: ?breast-fed = ?formula**

**Ha: ?breast-fed > ?formula**

**b) Test statistic:**

**Degrees of freedom:**

**P-value: 0.1236**

P-value > , i.e 0.1236 > 0.01, That is Fail to Reject Ho at 1% level of significance.

**ANSWER: C. Fail to reject the null hypothesis. There is not significant evidence that the mean hemoglobin level is higher among breast-fed babies.**

(b) Give a 95% confidence interval for the mean difference in hemoglobin level between the two populations of infants.

**(-0.433, 1.633)**

**B. We need two independent SRSs from normal populations.**

ANSWER: C. Fail to reject the null hypothesis. There is not significant evidence that the mean hemoglobin level is higher among breast-fed babies. (b) Give a 95% confidence interval for the mean difference in hemoglobin level between the two populations of infants. (X_1^bar - Y_1^bar) plusminus t_df,alpha/2 * squareroot S_1^2/n_1 + S_2^2/n_2 (13.3 - 12.7) plusminus t_39,0.05/2 * squareroot 1.6^2/22 + 1.7^2/20 (-0.433,1.633) B.

We need two independent SRSs from normal populations.