Methodology review: Assessing unidimensionality of tests and items
1985
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Methodology review: Assessing unidimensionality of tests and items
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1985
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Abstract
Various methods for determining unidimensionality
are reviewed and the rationale of these methods is assessed.
Indices based on answer patterns, reliability,
components and factor analysis, and latent traits are
reviewed. It is shown that many of the indices lack a
rationale, and that many are adjustments of a previous
index to take into account some criticisms of it. After
reviewing many indices, it is suggested that those
based on the size of residuals after fitting a two- or
three-parameter latent trait model may be the most
useful to detect unidimensionality. An attempt is made
to clarify the term unidimensional, and it is shown
how it differs from other terms often used interchangeably
such as reliability, internal consistency,
and homogeneity. Reliability is defined as the ratio of
true score variance to observed score variance. Internal
consistency denotes a group of methods that are
intended to estimate reliability, are based on the variances
and the covariances of test items, and depend on
only one administration of a test. Homogeneity seems
to refer more specifically to the similarity of the item
correlations, but the term is often used as a synonym
for unidimensionality. The usefulness of the terms internal
consistency and homogeneity is questioned. Unidimensionality
is defined as the existence of one latent
trait underlying the data.
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Hattie, John A. (1985). Methodology review: Assessing unidimensionality of tests and items. Applied Psychological Measurement, 9, 139-164. doi:10.1177/014662168500900204
Suggested citation
Hattie, John. (1985). Methodology review: Assessing unidimensionality of tests and items. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/102073.
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