Question: A developmental psychologist would like to determine how much fine motor skill improves for children from age 3 to age 4. A random sample of n = 15 3-year-old children and a second sample of n = 15 4-year-olds are obtained. Each child is given a manual dexterity test that measures fine motor skills. The average score for the older children was M = 40.6 with SS = 430 and the average for the younger children was M = 35.4 with SS = 410. Using these data,

a. Make a point estimate of the population mean difference in fine motor skills.

b. Make an interval estimate so you are 95% confident that the real mean difference is in your interval.