Jacob wants to know how many students in his school enjoy watching space travel programs on tv. he poses this question to all 20 students in his history class and finds that 80% of his classmates enjoy watching space travel programs on tv. he claims that 80% of the school's student population would be expected to enjoy watching space travel programs on tv. is jacob making a valid inference about this population?

no, it is not a valid inference because his classmates do not make up a random sample of the students in the school
no, it is not a valid inference because he asked all 20 students in his history class instead of taking a sample from his math class
yes, it is a valid inference because his classmates make up a random sample of the students in the school
yes, it is a valid inference because he asked all 20 students in his history class