Effectiveness is the extent to which an evaluand produces desired or intended outcomes. Effectiveness alone provides a poor assessment of overall evaluand merit or worth: It is possible for something to be “effective” (i.e., produce desirable intended outcomes) but at the same time produce serious detrimental, if unintended, effects. It is also possible for an evaluand to be highly effective but extremely inefficient or overly costly. Claims of effectiveness require the demonstration of a causal link between the evaluand and the desired changes to show that they are, in fact, outcomes caused by the evaluand and are not coincidental changes.