Excellent test-retest reliability does
not necessarily ensure that individuals'
repeated performance will be
consistent from test to test. Scores
may vary, given expected variability
of individual performance and measurement
error. A measure of absolute
variability provides useful inforinformation
to delineate the "expected"
changes from "trtie" changes in performance.
Statistically, absolute reliability
is determined by the standard
error of measurement (SEM), or the
standard deviation of the measurement
errors,"" and a clinically useftil
mechanism for looking at absolute
reliability is the minimal
detectable change (MDC) score