Reliability describes the precision of a measurement. This contribution begins by defining the concept of reliability and explaining why the reliability of a measurement is relevant. It then discusses the model assumptions that must be made in order to estimate the reliability of a measurement, and it presents five methods of estimating reliability: the test-retest method, the parallel-forms method, the split-half method, the internal consistency method, and the estimation of reliability using structural equation modelling. The contribution concludes with a brief outline of the commonalities and differences between classical test theory and the item response theory and the importance of these theories for the estimation of reliability.
Danner, D. (2016). Reliability – The precision of a measurement. GESIS Survey Guidelines. Mannheim, Germany: GESIS – Leibniz Institute for the Social Sciences. doi: 10.15465/gesis-sg_en_0113