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Q.103

Expert-verifiedFound in: Page 554

Book edition
OER 2018

Author(s)
Barbara Illowsky, Susan Dean

Pages
902 pages

ISBN
9781938168208

La Leche League International reports that the mean age of weaning a child from breastfeeding is age four to five worldwide. In America, most nursing mothers wean their children much earlier. Suppose a random survey is conducted of 21 U.S. mothers who recently weaned their children. The mean weaning age was nine months (3/4 year) with a standard deviation of 4 months. Conduct a hypothesis test to determine if the mean weaning age in the U.S. is less than four years old.

(0.60 years, 0.90 years) or approximately (7.2 months, 10.8 months), when the sample standard deviation is rounded to 0.33.

${H}_{0}:\mu =4;{H}_{a}:\mu <4$

Normal: $N\left(4,\frac{0.333}{\sqrt{21}}\right)$

Test Statistic: $t=\u201344.7$

$p-value=0.0000$

In one to two complete sentences, explain what the p-value means for this problem.

If the null hypothesis is true (the mean age is 4), then there is a 0.0000 probability that the sample (estimated) mean age is 3 or more.

alpha | decision | reason for decision |

0.01 | Reject the null hypothesis. | $p-value<0.01$ |

Conclusion: There is sufficient evidence to conclude that the mean age at which American mothers wean their children is less than four years old.

(0.60 years, 0.90 years) or approximately (7.2 months, 10.8 months), when the sample standard deviation is rounded to 0.33.

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