For one academic year all the students at a high school were observed. The aim was to test the hypothesis that studying more increased a student' s chances of earning a higher grade. It turned out that the students who spent the most time studying did not earn grades as high as did many students who studied less. Nonetheless, the researchers concluded that the results of the observation supported the initial hypothesis.
The statement 'In each course, the more a student studied, the better his or her grade was in that course' most helps to explain why the researchers drew the conclusion described above.