Homework creates a bridge between school and home. Parents rarely get to spend much time with you while you're at school. Homework allows them to keep up with what you're doing in your classes on a daily basis. But you don't have homework purely for your parents' benefit. It's good for you, too, or maybe because teachers want to see us suffer
Answer: Tammy's sample may not be vaild because she surveyed the students only from her class and it is likely that other classes might not like the subject maths. She might get the accurate results by surveying a larger number of people in the school instead of just her class.
