Reliability Flashcards
Classical test theory (CTI)
A measurement theory that defines the conceptual basis of reliability and outlines procedures for estimating reliability of psychological measures
What does a test’s reliability reflect?
The extent to which differences in respondent’s scores are a function of their true psychological differences
Observed scores
the values obtained from measuring a characteristic in a sample of individuals
True scores
the real amounts of that characteristic in that sample of individuals
Reliability
the extent to which differences in respondent’s observed scores are consistent with differences in their true scores
What does reliability for a measurement procedure depend on?
The extent to which differences in observed scores can be attributed to differences in their true scores
Measurement error
The difference between observed and true scores
Reliability =
signal/signal+noise
Reliability depends on -
- the extent to which differences in scores can be attributed to inter-or-intraindividual differences
- the extent to which differences in scores are a function of measurement error
In CIT observed scores on a test is
a function of true score plus error
Xo
observed test score
Xt
true score
Xe
error
CIT assumption error
measurement error is equally likely to inflate/deflate any particular score
Important consequences of CIT assumption
- error tends to cancel itself out across respondents
- error scores are uncorrelated with true scores
Se
error score variance
Xe
error scores
A high degree of error variance =
potentially poor measurement
