A comprehensive study conducted by the National Institute of Child Health and Human Development tracked more than 1,000 children from an early age through elementary school (New York Times, November 1, 2005). The study concluded that children who spent more than 30 hours a week in child care before entering school tended to score higher in math and reading when they were in the third grade. The researchers cautioned that the findings should not be a cause for alarm because the differences were found to be small. Explain how the difference between the mean math score for the child care group and the overall mean for third graders could be small but the researchers could still reach the conclusion that the mean for the child care group is significantly higher than the overall mean.