Question

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.

Answer 1

I believe there is something wrong with the experiments.

First of all, there is no control group  which make the researcher able to distinguish which variables are the one that would change the nature of independent variable. The second reason is because there is biased or non representative sample in the study ( only from colleagues in the same field)