Causality requires three
conditions: (1) covariation of cause and effect (i.e., if cause happens, then effect also happens;
and if cause does not happen, effect does not happen), (2) temporal precedence: cause mustprecede effect in time, (3) no plausible alternative explanation (or spurious correlation).
Certain research designs, such as laboratory experiments, are strong in internal validity by
virtue of their ability to manipulate the independent variable (cause) via a treatment and
observe the effect (dependent variable) of that treatment after a certain point in time, while
controlling for the effects of extraneous variables.