Consider the following scenarios and explain why the correlation described need not imply that one factor causes the other. Be explicit about the other factors that might be at play.

a. Students in charter schools have higher test scores than their counterparts in nearby public schools.

b. A negative correlation between maternal smoking and their children's birth weight.

c. On average, students with relatively large student loans are less likely to default.

d. Within a school, students in smaller classes have lower 1 2 end of year test scores. e. Children in families that spend more time on educational activities do not have better educational outcomes than children in families who spend less time on educational activities.