Diagnostic reading tests, in contrast to achievement
tests, claim to measure specific components of ability
hypothesized to be important for diagnosis or remediation.
A minimal condition for demonstrating the construct
validity of such tests is that they are able to differentiate
validly between the reading traits that they
claim to measure (e.g., comprehension, sound discrimination,
blending). This condition is rarely tested,
but multitrait-multimethod (MTMM) designs are
ideally suited for this purpose. This is demonstrated in
two studies based on the 1966 version of the Stanford
Diagnostic Reading Test (SDRT). In each study, the
application of the Campbell-Fiske guidelines and confirmatory
factor analysis (CFA) to the MTMM data indicated
that the SDRT subscales could be explained in
terms of a method/halo effect and a general reading
factor that was not specific to any of the subscales;
this refutes the construct validity of the 1966 version
of the SDRT as a diagnostic test. Other diagnostic
tests probably suffer the same weakness and should
also be evaluated in MTMM studies.
Marsh, Herbert W & Butler, Susan. (1984). Evaluating reading diagnostic tests: An application of confirmatory factor analysis to multitrait-multimethod data. Applied Psychological Measurement, 8, 307-320. doi:10.1177/014662168400800308
Marsh, Herbert W.; Butler, Susan.
Evaluating reading diagnostic tests: An application of confirmatory factor analysis to multitrait-multimethod data.
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