Question

: Following are weights, in pounds, of

11

two-month-old baby girls. It is reasonable to assume that the population is approximately normal.

12.34	9.34	8.51	11.87	8.63	12.32
12.23	12.95	10.30	11.48	8.51

Construct a

99.8%

interval for the mean weight of two-month-old baby girls. Round the answers to three decimal places.

Answer 1

Confidence interval for Population mean is given as below:

Confidence interval = Xbar ± t*S/sqrt(n)

From given data, we have

Xbar = 10.77090909

S = 1.747171741

n = 11

df = n – 1 = 10

Confidence level = 99.8%

Critical t value = 4.1437

(by using t-table)

Confidence interval = Xbar ± t*S/sqrt(n)

Confidence interval = 10.77090909 ± 4.1437*1.747171741/sqrt(11)

Confidence interval = 10.77090909 ± 2.1829

Lower limit = 10.77090909 - 2.1829 = 8.588

Upper limit = 10.77090909 + 2.1829 = 12.954

Confidence interval = (8.588, 12.954)