Dr Paddock Is a Counseling Psychologist Who Is Interested in Decreasing

Essay

Dr. Paddock is a counseling psychologist who is interested in decreasing adjustment issues in first-year college students. She is curious if having students create collages of their first few weeks of school and then mail them home will help students feel they have integrated their new life with their old and, as a result, will help them feel less homesick. She samples a group of 100 incoming college freshmen at her university and measures how homesick they are during the first week of school. During week 4 of school, she has them make the collage and send it home. During week 7 of school, she measures their homesickness again. She notices a significant reduction in the amount of homesickness from the pretest to the posttest and concludes that her treatment is effective.
Name two threats to internal validity that are likely to be present in Dr. Paddock's study, given her particular design. What other explanation do these threats provide for the results found by Dr. Paddock?