1. A study was conducted to assess the effects of free, out-of-class statistics tutoring on the academic performance of students in this course. A subset of students voluntarily enrolled in this tutoring, and they were compared with the rest of the class. Students were assessed based on the final course grade. Results indicated that tutoring was beneficial, as students who received it performed better than the others (based on differences in final grades between the two groups).

1. Is this a true experiment, quasi-experiment, or non-experiment? (2)
2. What is the term for this kind of design (e.g., One-Group Pre-Test Posttest)? (2)
3. For this study, identify and clearly describe important potential "Multiple-Group" threats to internal validity. (4)
4. Clearly describe and justify an improved approach to assessing the same research question. (4)