A psychologist has developed a standardized test for measuring vocabulary skills in 4-year-old children. The scores on the test form a normal distribution with = 60 and = 10.A researcher would like to use this test to investigate the hypothesis that children who grow up as single children develop vocabulary skills at a faster rate than children in larger families.A sample of n = 25 single children is obtained, and a mean test score for this sample is X = 63.

Using a 95% Confidence Interval is there a difference between single children's vocabulary development and children from larger families' vocabulary development?