* The student's personality and learning style: Some students are naturally more proactive and diligent.
* The subject matter: Students might study more for a challenging subject they find difficult.
* The importance of the exam: A final exam will likely see more studying than a small quiz.
* The student's prior academic performance: Students who are already doing well might study less.
* The perceived difficulty of the exam: Rumors or past experiences can influence how much students study.
* Time management skills: Some students might procrastinate and cram, while others plan their studying effectively.
While studies on student behavior exist, it's impossible to give a definitive percentage. Any number would be a broad generalization and likely inaccurate.