[05/22/2024] Reliability
Last updated
Last updated
Coefficient alpha and the internal structure of tests
Abstract
A general formula (α) of which a special case is the Kuder-Richardson coefficient of equivalence is shown to be the mean of all split-half coefficients resulting from different splittings of a test. α is therefore an estimate of the correlation between two random samples of items from a universe of items like those in the test. α is found to be an appropriate index of equivalence and, except for very short tests, of the first-factor concentration in the test. Tests divisible into distinct subtests should be so divided before using the formula. The index𝑟¯𝑖𝑗, derived from α, is shown to be an index of inter-item homogeneity. Comparison is made to the Guttman and Loevinger approaches. Parallel split coefficients are shown to be unnecessary for tests of common types. In designing tests, maximum interpretability of scores is obtained by increasing the first-factor concentration in any separately-scored subtest and avoiding substantial group-factor clusters within a subtest. Scalability is not a requisite.
Main point
Introduces Cronbach's alpha, a measure of internal consistency reliability for a set of items or test scores.
Making sense of Cronbach's alpha
Main point
A practical guide to understanding and interpreting Cronbach's alpha.
The Design and Analysis of Clinical Experiments
Main point
Discusses the design and analysis of studies involving repeated measures, including test-retest reliability.
Measurement error in psychological research: Lessons from 26 research scenarios
Main point
Provides a detailed discussion of measurement error and its implications for test-retest reliability.
A coefficient of agreement for nominal scales.
Main point
Introduces Cohen's kappa, a statistical measure of inter-rater reliability for categorical data.
Intraclass correlations: Uses in assessing rater reliability.
Main point
Discusses intraclass correlation coefficients (ICCs) and their use in assessing inter-rater reliability.
Scale reliability, Cronbach’s coefficient alpha, and violations of essential tau-equivalence with fixed congeneric components
Abstract
The population discrepancy between Cronbach's Coefficient Alpha and scale reliability with fixed congeneric measures, uncorrelated errors, and sampling of subjects is studied. This difference is expressed in terms of individual component violations of the assumption of essential T-equivalence that is necessary and sufficient for Alpha to equal composite reliability. An upper bound of the discrepancy is obtained and its magnitude assessed in practical contexts of informed scale development. As an alternative when the difference may be considerable, a latent variable model is recommended for estimating scale reliability.
Test Theory: A Unified Treatment
Book review