What characteristic defines reliable instruments?

Reliable instruments are defined by their ability to yield consistent results upon repetition. This means that when the same measurement is taken multiple times under similar conditions, the results should be very similar or the same, demonstrating stability and dependability of the measurement process. Reliability is crucial in any assessment or testing scenario because it ensures that the outcomes are not influenced by random errors or fluctuations. This consistency is what allows practitioners to trust the data collected from these instruments, leading to accurate interpretations and conclusions.

In contrast, instruments that produce different results each time fail to demonstrate reliability, as inconsistency undermines the validity of the assessment process. Similarly, while specificity to the individual being assessed is a valuable characteristic for some assessments, it does not inherently contribute to the reliability of the instrument itself. Lastly, requiring validation for each use refers to the need for confirming the appropriateness and accuracy of an instrument in specific situations, which relates more to its validity rather than its reliability. Thus, consistent results are key to defining the reliability of an assessment tool.