What indicates the reliability of an instrument according to reliability coefficients?

Reliability coefficients are statistical measures used to assess the consistency and stability of a measurement instrument over time or across different conditions. A score between 0 and 1 is an appropriate range for reliability coefficients. Values close to 1 indicate high reliability, suggesting that the instrument produces consistent results during repeated measurements or assessments.

For example, a reliability coefficient of 0.9 would imply excellent consistency, while a coefficient of 0.5 indicates poor reliability. Coefficients below zero suggest that the instrument is worse than random guessing, which is not desirable for research or clinical application.

In contrast, a reliability score higher than 1 is not possible in standard contexts, as it would suggest a level of reliability that surpasses perfect consistency, which is unattainable. Likewise, a reliability score of exactly 0 indicates no reliability, meaning that the instrument does not provide any consistent information. Lastly, a score of 2 or higher is not meaningful in the context of reliability coefficients, as they do not exceed 1 in established statistical practices. Thus, the only correct and feasible indication of reliability is a score between 0 and 1.