On the Difference Between Reliability of Measurement and Precision of Survey Instruments

Despite the importance of assessing the reliability of evaluative measures, there is a confusing array of conceptual scheme, and coefficients for calculating "the reliability" of an item or scale. In particular, reliability may be conceived of and estimated from a true-score model or a sampling precision perspective. The former model is associated with such estimates as parallel or alternate forms reliability, split-half reliability, and coefficient alpha, the latter with standard error, coefficient of variation, and confidence intervals for observed scores.

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