A study was conducted using a sample of 645 students. The students in the study were all 1st semester graduate students and were distributed across 7 University departments. Students were randomly distributed to 3 groups.
Over the first 5 weeks of a semester, group 1 was given easy problem assignments, group 2 received moderately difficult problem assignments, and group 3 received very difficult assignments.
The groups were then compared on their self-ratings of the usefulness of statistics.
No attempt was made to assess or control for student differences in math background. Some students received special statistics tutoring during the 1st 5 weeks of the semester unbeknownst to the researcher.
4. Discuss potential threats to internal validity posed by this study.
5. Describe two ways to deal with the threats discussed in a.
6. Discuss potential threats to external validity posed by this study.
7. Describe two ways to deal with the threats discussed in c.
8. A research design may include one or both of these random procedures: (i) random sampling from some specified existing population and (ii) random assignment of experimental participants to treatment levels within the experiment.
Discuss how the use of each of these procedures contributes to the meaningfulness and interpretation of the research outcome.