Question: A psychologist claims that the mean age at which children being walking is 12.5 months. To test this claim a researcher took a random sample of 20 children and found that the mean age at which they began walking is 12.9 months with a standard deviation of .80 month. At the alpha= .01 significance level, can we conclude that the mean age at which all children begin walking is different from 12.5 months?