Every correlational finding has three alternative explanations: reverse causation, a third variable, or chance. Saying 'X causes Y' from a correlation is the single most common violation of psychological reasoning.
The collection makes this the spine of its research-methods unit. Correlation measures association; only a true experiment — with manipulation of the IV, random assignment, and a control group — can license a causal claim. Students who internalize this cheat-sheet stop falling for the 'breakfast boosts grades' headline class of errors.

