PSYCHOLOGY PSYC 515 TRAINING STUDY
SHEET 2026 UPDATED QUESTIONS AND
ANSWERS
◉T Answer: true score; if there were no error in measurement, this
would be the true score
mean of the observed score over an infinite number of
administrations
◉E Answer: random error
all the random error that is not systematic; can hurt or help score
◉assumptions of CTT Answer: mean of error scores = zero
error scores on two different tests are uncorrelated
correlation between T and e is zero
variance across people
◉sigma squared x Answer: observed score variability
◉sigma squared x = Answer: sigma squared t + sigma squared e
,◉just like observed scores, true scores also... Answer: differ because
of measurement error and error variance
◉error variance Answer: variability in how error affected the results
of the test for different people
◉bigger error variability = Answer: bigger influence on how error
affected scores
◉when reliability = 1 Answer: reliability is perfect
no measurement error
X=T
◉when reliability = 1, all observed score variance = Answer: true
score variance
all differences between observed scores reflect differences in true
scores
◉when reliability = 1, the correlation between Answer: observed
scores and true scores is 1
observed scores and error scores is 0
◉when reliability is 0 Answer: only random error is included in
measurement X=e
, ◉when reliability is 0, all observed score variance = Answer: error
variance
◉when reliability is 0, all differences between observed scores
reflect Answer: error of measurement
◉when reliability is 0, the correlation between... Answer: observed
scores and true scores is 0
observed scores and error scores is 1
◉when 0 < rxx < 1 Answer: the measurement includes some error
observed score variance includes both true score variance and error
variance
differences in their true scores and differences in the amount of
error they experienced in their test administration
◉when 0 < rxx < 1, reliability is the proportion of Answer: observed
score variance that is due to true score variance (theoretical
equation because we can't know the true score variance)
◉how much error do you consider acceptable in your measure?
Answer: 40% of error is acceptable, meaning reliability of .60
SHEET 2026 UPDATED QUESTIONS AND
ANSWERS
◉T Answer: true score; if there were no error in measurement, this
would be the true score
mean of the observed score over an infinite number of
administrations
◉E Answer: random error
all the random error that is not systematic; can hurt or help score
◉assumptions of CTT Answer: mean of error scores = zero
error scores on two different tests are uncorrelated
correlation between T and e is zero
variance across people
◉sigma squared x Answer: observed score variability
◉sigma squared x = Answer: sigma squared t + sigma squared e
,◉just like observed scores, true scores also... Answer: differ because
of measurement error and error variance
◉error variance Answer: variability in how error affected the results
of the test for different people
◉bigger error variability = Answer: bigger influence on how error
affected scores
◉when reliability = 1 Answer: reliability is perfect
no measurement error
X=T
◉when reliability = 1, all observed score variance = Answer: true
score variance
all differences between observed scores reflect differences in true
scores
◉when reliability = 1, the correlation between Answer: observed
scores and true scores is 1
observed scores and error scores is 0
◉when reliability is 0 Answer: only random error is included in
measurement X=e
, ◉when reliability is 0, all observed score variance = Answer: error
variance
◉when reliability is 0, all differences between observed scores
reflect Answer: error of measurement
◉when reliability is 0, the correlation between... Answer: observed
scores and true scores is 0
observed scores and error scores is 1
◉when 0 < rxx < 1 Answer: the measurement includes some error
observed score variance includes both true score variance and error
variance
differences in their true scores and differences in the amount of
error they experienced in their test administration
◉when 0 < rxx < 1, reliability is the proportion of Answer: observed
score variance that is due to true score variance (theoretical
equation because we can't know the true score variance)
◉how much error do you consider acceptable in your measure?
Answer: 40% of error is acceptable, meaning reliability of .60
