Final answer:
In the given experiment, the independent variable is the provision of daily cookies to one of the psychological classes to determine its effect on students' final grades.
Step-by-step explanation:
A researcher wants to conduct an experiment to determine if eating a cookie before class each day improves students' grades. He uses two psychological classes for the experiment, providing daily cookies to one and nothing to the other. At the end of the semester, the researcher compares the final grades of the students in the two classes. The independent variable in this experiment is providing daily cookies, which is the factor that the researcher manipulates to see if it brings about a change in the dependent variable, which in this case, are the students' final grades. Therefore, the correct answer to this question is option 2) Providing daily cookies.