Professor jones wants to study vocabulary growth in preschool children. he contacts all his faculty colleagues who have children, and from this group he assembles a sample of 20 faculty children ranging in age from 2 to 5 years. to test each child's word knowledge, professor jones reads the child a list of simple words he has gathered from children's storybooks and records whether the child understands each word. he then uses the results to publish norms (standard or expected levels of achievement) for vocabulary mastery for each year, from 2 to 5 years of age.