6. A true score is
the expected
value for the
distribution of
possible scores
for an
individual.
Population Mean
Mean for a
Specific Person
Source: W.J Schneider (2019)
7. Observed Score True Score Measurement Error
Hypothetical average of
many measurements
free of carryover effects
Deviations from
the True Score
15. Errors have an expected value of 0.
Observed scores and true scores have the same expected value.
Errors are uncorrelated with true scores.
Observed Score True Score Measurement Error
Errors are uncorrelated with each other.
Observed variance is the sum of true score and error variance.
16. Typical Distance of an Observed Score
from its True Score
Standard Error of Measurement
17. Test – Retest Reliability
• The same test is given two times
at different time.
• The correlation of the two
results of the same test is known
as test – retest reliability
Covariance
Geometric Mean
of the Variances
19. Cronbach’s α
The Mean of All Possible
Split-Half Correlations,
Corrected for Test Length
Accurate for parallel and true-score equivalent tests
Underestimates the reliability of congeneric tests
Overestimates the reliability of multifactorial data
