Final answer:
The percentage of North American mothers who continue to breastfeed their babies at 4 to 6 months can vary. A hypothesis test can determine if the mean weaning age in the United States is less than four years old.
Step-by-step explanation:
The percentage of North American mothers who continue to breastfeed their babies at 4 to 6 months can vary. However, according to the La Leche League International, the mean age of weaning a child from breastfeeding is age four to five worldwide. In the United States, most nursing mothers wean their children much earlier. A random survey of 21 U.S. mothers who recently weaned their children found that the mean weaning age was nine months (3/4 year) with a standard deviation of 4 months. In order to determine if the mean weaning age in the United States is less than four years old, a hypothesis test needs to be conducted.