Question

Child Health and Development Studies (CHDS) has been collecting data about expectant mothers in Oakland, CA since 1959. One of the measurements taken by CHDS is the weight increase (in pounds) for expectant mothers in the second trimester. In a fictitious study, suppose that CHDS finds the average weight increase in the second trimester is 14 pounds. Suppose also that, in 2015, a random sample of 40 expectant mothers have mean weight increase of 16 pounds in the second trimester, with a standard deviation of 6 pounds. At the 5% significance level, we can conduct a one-sided T-test to see if the mean weight increase in 2015 is greater than 14 pounds. Statistical software tells us that the p-value= 0.021.

Which of the following is the most appropriate conclusion?

A. There is a 2.1% chance that a random sample of 40 expectant mothers will have a mean weight increase of 16 pounds or greater if the mean second trimester weight gain for all expectant mothers is 14 pounds
B. There is a 2.1% chance that mean second trimester weight gain for all expectant mothers is 14 pounds in 2015
C. There is a 2.1% chance that mean second trimester weight gain for all expectant mothers is 16 pounds in 2015
D. There is 2.1% chance that the population of expectant mothers will have a mean weight increase of 16 pounds or greater in 2015 if the mean second trimester weight gain for all expectant mothers was 14 pounds in 1959.

Answer 1

a. There is a 2.1% chance that a random sample of 40 expectant mothers will have a mean weight increase of 16 pounds or greater if the mean second trimester weight gain for all expectant mothers is 14 pounds

Explanation:

Since we have to test that whether the mean weight is greater than 14 pounds, so test is right tailed and if ta is the value of test static then p-value is P(t> t_a ) . Where t_a={16-14\over 6/\sqrt {40}} .

Now p-value is 0.021.

So the correct conclusion is

There is a 2.1% chance that a random sample of 40 expectant mothers will have a mean weight increase of 16 pounds or greater if the mean second trimester weight gain for all expectant mothers is 14 pounds