A biased example: Asking students who are in line to buy lunch
An unbiased example: Asking students who are leaving/going to lunch(<em>NOT buying </em><em>lunch</em><em />).
But in this case, the answer choices can be... confusing. Don't panic! You're given numbers and, of course, your use of logic.
Answer choice A: 100 students grades 6-8 Answer choice B: 20-30 students any <em>one</em> grade<em></em><em> </em>Answer choice C: 5 students <em></em>Answer choice D: 50 students grade 8
An unbiased example would be to choose students from <em>any grade.</em> So we can eliminate choices B and D.
Now, the question wants to <em>estimate how many people at your middle school buy lunch.</em> This includes the whole entire school, and if you are going to be asking people, you aren't just going to assume that if 5 people out of 5 people you asked bought lunch, the whole school buys lunch.
So, to eliminate all bias and/or error by prediction, answer choice A, the most number of students, is your answer.
