Question

Carla wants to know how many students in her school enjoy watching reality TV shows. She asks all 22 students in her science class and finds that 40% of her classmates enjoy watching reality TV shows. She claims that 40% of the school's student population would be expected to enjoy watching reality TV shows. Is Carla making a valid inference about her population? No, it is not a valid inference because she asked all 22 students in her science class instead of taking a sample from her music class No, it is not a valid inference because she asked all 22 students in her science class instead of taking a sample of the students in her school Yes, it is a valid inference because she asked all 22 students in her science class Yes, it is a valid inference because her classmates make up a random sample of the students in the school

Answer 1

Statistic significance requires that your sample be representative of the population, but I'm struggling with this because if the class is an elective then the answer would be: No, it is not a valid inference because she asked all 22 students in her science class instead of taking a sample of the students in her school.
BUT if the class is required, as most science classes are, then it WOULD be a random sample of the school. So the last option would be correct. 

My guess though is that the teacher is looking for answer B.