An experiment is designed to compare the differences in learning outcomes between learning math from a video game and learning it from traditional classroom activities. the experiment finds no difference between the two. what was the independent variable in this experiment?

In this case, the independent variables are Classroom activities and video games.

Independent variable refers to the variables which outcome are not depended on other variables (and the dependent variable is the exact opposite)

In this particular case, the only dependent variables are the learning outcome.