Question

can you paraphrase below please! thank you!

"Not necessarily, because in statistics correlation does not cause and effect relationship. Better school, such as quality of the teachers and resources provided to the students, may be more likely have smaller classes; while the better students may also choose to attend better schools. That is there is a two-way selection in the issue of class size and student performance. Therefore, the negative relationship estimated in part (b) may only reflect the students in the small classes are smarter."

Answer 1

It implies that that Correlation indicates the cause and effect relationship , it means that change in one causes the change in the other. But it is not necessarily true that correlation shows the cause and effect relationship.

Like, better schools can have small size of class .

And better students attend better schools.

It means there is two-way relationship in the issue of class size and students performance. Smaller the size of classes , then there can be more focus on students , so the better the students performance.