Dr. Paddock is a counseling psychologist who is interested indecreasing adjustment issues in first-year college students. She iscurious if having students create collages of their first few weeksof school and then mailing them home will help students feel theyhave integrated their new life with their old and, as a result,will help them feel less homesick. She samples a group of 100incoming college freshmen at her university and measures howhomesick they are during the first week of school. During Week 4 ofschool, she has them make the collage and send it home. During Week7 of school, she measures their homesickness again. She notices asignificant reduction in the amount of homesickness from thepretest to the posttest and concludes that her treatment iseffective.
Name two threats to internal validity that are likely to bepresent in Dr. Paddock’s study, given her particular design. Whatother explanation do these threats provide for the results found byDr. Paddock?
