RELIABILITY AND VALIDITY

The psychometric properties of reliability and validity and the procedures used to assess them are conceptually described in this chapter. The part devoted to the reliability, or test score accuracy, is focused in the models, procedures and statistical indicators most usually employed. As to validity, the most important psychometric property, and the one whose conception has changed the most, we summarize its history in testing contexts. The reader is prevented that reliability and validity are not, as usually thought, properties of the testing instruments but of the particular inferences made from the scores. Another common error is considering reliability and validity, not as questions of degree, but as absolute properties.