Final answer:
A valid outcome measure accurately assesses what it is designed to assess, reflecting the true scope of the concept being measured in a consistent and correct manner.
Step-by-step explanation:
When an outcome measure is shown to be valid, it means that it accurately measures what it is intended to measure. Validity is a critical aspect of measurement that indicates the degree to which a given instrument or tool accurately captures the concept it is supposed to measure. The various types of validity, such as construct validity, are essential to ensure that the results are not only consistent but also correct and representative of the intended measurement. By comparison, while reliability pertains to the consistency of a measure to produce the same results under the same circumstances, it does not encapsulate whether the results are actually correct. An operational definition, used to define concepts in measurable terms, must be both valid and reliable in order to yield meaningful and consistent results across different contexts or studies. Therefore, for an outcome measure to be considered valid, it must reflect the true scope of the concept being measured and do so in a replicable and accurate manner.