Restricted range phenomenon 3. The fact that correlation does not imply causation. Correlation is necessary but not sufficient for demonstrating causality. B causes A 3. A and B are both related to a third variable that causes them both.
Family income correlates with lead exposure in children.
Annual oil production is related to the size of the world's population. Children who watch more violent TV are more aggressive. Number of churches in a town is related to the number of bars. Parents who use more physically punitive means of control have children who are more aggressive.