Reliability of measures. Measures that have low reliability make it difficult to detect true changes and may make an effective intervention appear ineffective. Example: Ryan used a measure of...

Reliability of measures. Measures that have low reliability make it difficult to detect true changes and may make an effective intervention appear ineffective. Example: Ryan used a measure of selfesteem with test–retest reliability of only .40. Although the client’s self-esteem actually changed over time, Ryan couldn’t tell with his measure whether the change was real or merely a reflection of an unstable measure.