How is "reliability" defined in the context of testing and observation?

Reliability in the context of testing and observation refers to the consistency of a test's results upon repeated trials. This means that if the same test is administered multiple times under the same conditions, it should produce similar results each time. High reliability indicates that the test measures consistently over time and across different instances, minimizing the influence of random error. This concept is crucial because it ensures that the findings can be trusted and are stable, which is essential for making informed decisions based on the test outcomes.

In contrast, aspects like the accuracy of a measure, the relevance to observed behavior, or the ease of understanding outcomes are important factors in evaluating tests but do not directly pertain to reliability. Reliability specifically emphasizes the stability and consistency of the results rather than how accurate or relevant a test might be, or how easily the results can be comprehended.