Suppose your lecturer splits the students in class into two groups: students on the left and students on the right. If and represent the proportion of students who own an Apple product on the left and right, respectively, would you be surprised if did not exactly equal ?
Answer. While the proportions would probably be close to each other, it would be unusual for them to be exactly the same. We would probably observe a small difference due to chance.
If we don’t think the side of the room a person sits on in class is related to whether the person owns an Apple product, what assumption are we making about the relationship between these two variables?
Answer. We would be assuming that these two variables are independent.