In a study, parents were asked to rate each television program that their children watched.
Given that ...
Parents rated the violence of each TV show their kids watched on a 1 - 5 scale.
and that ..
The number of times kids were disciplined in school was also recorded.
How can we explain that ..
Kids who watched programs ranked 3-5 were 50% more likely to have been disciplined than other children.
Evaluate / Goal
We need ways to explain why there's a correlation between more violent shows and being disciplined in school (the causality could flow in either direction, or they could both be symptoms of a third factor).
Those explanations assume that shows ranked 3-5 really were more violent. But it's possible that they weren't; it's just that the parents were more sensitive to violence and ranked them higher. So we could also explain these facts by some relationship between and "kids getting disciplined in school."