At one large university, a group of education specialists wanted to test the effectiveness of a newly designed academic improvement course. students seeking academic at the university counseling center were asked to participate in this 6-week program. only students who were judged to have deficiencies in reading comprehension and other study-related skills were chosen for the program. students whose academic problems were judged to be the result of emotional difficulties of one sort or another were not enrolled in the program but were counseled in a manner more appropriate to their problem. a group of 30 students completed the program at the counseling center. a review of grades and teachers' comments revealed that a large majority of the students were doing better in school after completing the program than before. the difference between pre-program and post-program performance measures was statistically significant. identify two major threats to the internal validity of this study as it has been described. for each threat identified explain why there is another plausible hypothesis for the obtained effect other than that based on the effectiveness of the academic improvement course.