To determine whether speed-reading influences reading comprehension, a researcher obtains two reading comprehension scores for each student in a group of high school students, once before and once after training in speed-reading. Another investigator criticizes the design of the previous study, saying that high school students should have been randomly assigned to either the special training condition or a control condition and tested just once at the end of the study. Subsequently, she conducts this study.
Is the subsequent test quantitative or qualitative? What would be the the best/most precise form to test the second study (t , F , or x2 tests)?