After they had failed in the writing exam that was required for all students before graduation,15 students were placed in a class in which they received additional tutoring.After completing this class,all 15 students retook the exam and earned higher scores.Their success was held up as an example that the class curriculum really works.What source of internal invalidity has not been considered?
A)history effect
B)noncomparable groups
C)contamination
D)regression

Question

Quizplus · Accepted Answer

The source of internal invalidity that has not been considered is regression. This is because the students who scored poorly on the first exam were selected for the additional tutoring class, and it is likely that they would have improved their scores on the second exam even without the additional tutoring due to regression to the mean. Therefore, the improvement in scores cannot be solely attributed to the effectiveness of the class curriculum.

After They Had Failed in the Writing Exam That Was