Question

15) 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 8 months (2/3 year) with a standard deviation of 2 months. Conduct a hypothesis test to determine if the mean weaning age in the U.S. is less than four years old. Conduct a hypothesis test at the 5% level.

Note: If you are using a Student's t-distribution for the problem, you may assume that the underlying population is normally distributed. (In general, you must first prove that assumption, though.)

Explain what the p-value means for this problem.

• If H0 is false, then there is a chance equal to the p-value that the average age at which American mothers wean their children is equal to the sample mean or less.

• If H0 is true, then there is a chance equal to the p-value that the average age at which American mothers wean their children is equal to the sample mean or less.    

• If H0 is false, then there is a chance equal to the p-value that the average age at which American mothers wean their children is equal to the sample mean or more.

• If H0 is true, then there is a chance equal to the p-value that the average age at which American mothers wean their children is equal to the sample mean or more.

b) Sketch a picture of this situation. Label and scale the horizontal axis and shade the region(s) corresponding to the p-value.

Answer 1

the p-value means for this problem.:

If H0 is true, then there is a chance equal to the p-value that the average age at which American mothers wean their children is equal to the sample mean or less.   

is the correct option.

b)