Theories of Reliability and Validity

Theories of reliability and validity relate to how well a test or measurement accurately and consistently measures what it intends to. Reliability means the results are stable and consistent over time or different conditions. Validity indicates the test actually measures what it’s supposed to measure. For example, a bathroom scale is reliable if it shows the same weight each time, and valid if it accurately reflects your true weight. Both are essential for trustworthiness: reliability ensures consistency, while validity confirms accuracy. Together, they help determine whether a measurement is meaningful and useful.