The mean weight for a 2-year old child is = 26 pounds. The distribution of weights is normal with = 4 pounds.

The research would like to obtain a sample of n = 16 newborn infants and give their parents detailed instructions for stimulating their babies, since stimulation may effect development. One way we can measure infant development is by examining their body weight. At age 2, each infant will be weighed, and the mean weight will be computed.

If the mean weight for the sample is noticeably different from the mean for the general population, then the researcher can conclude that the stimulation had an effect on body weight. Although we don't know the actual mean for the population of stimulated infants, we can use the sample of n = 16 newborns to draw inferences about the unknown population.