Kali is an educational psychologist interested in the link between diet and grade point average (GPA). In particular, she wants to know whether vegetarians outperform non-vegetarians in college. She finds 30 vegetarian and 30 non-vegetarian undergraduate students on her campus and asks them to tell her their GPA. Her results show that the vegetarians' GPAs are significantly higher than the non-vegetarians' GPAs.

c. Did Kali's study establish the temporal-precedence criterion of causa tion? Explain your answer.