The purpose of this study is to describe and compare
the methods used by Thorndike, Thurstone, and
Rasch for calibrating test items. Thorndike and Thurstone
represent a traditional psychometric approach to
this problem, whereas Rasch represents a more modem
conceptualization derived from latent trait theory.
These three major theorists in psychological and educational
measurement were concerned with a common
set of issues that seem to recur in a cyclical manner in
psychometric theory. One such issue involves the invariance
of item parameters. Each recognized the importance
of eliminating the effects of an arbitrary sample
in the estimation of item parameters. The differences
generally arise from the specific methods chosen
to deal with the problem. Thorndike attempted to
solve the problem of item invariance by adjusting for
mean differences in ability distributions. Thurstone extended
Thorndike’s work by proposing two adjustments
which included an adjustment for differences in
the dispersions of ability in addition to Thorndike’s
adjustment for mean differences. Rasch’s method implies
a third adjustment, which involves the addition
of a response model for each person in the sample.
Data taken from Trabue (1916) are used to illustrate
and compare how Thorndike, Thurstone, and Rasch
would approach a common problem, namely, the calibration
of a single set of items administered to several
Engelhard, George. (1984). Thorndike, Thurstone, and Rasch: A comparison of their methods of scaling psychological and educational tests. Applied Psychological Measurement, 8, 21-38. doi:10.1177/014662168400800104
Engelhard, George, Jr..
Thorndike, Thurstone, and Rasch: A comparison of their methods of scaling psychological and educational tests.
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