M&D3 Week 1 Flashcards
Reliability
the consistency of a measurement repeated within a person or in a sample
test score
X = T + E
T (true score) is not known, E (error) is only estimated (X = the obtained score)
Accidental measurement errors (unpredictable)
Something you can’t predict beforehand, time of day, headache
Systematic measurement errors (constant)
Something you can predict beforehand, happens systematically
Confidence interval formula
CI = X +/- z * SE
X = score; z = standardized coefficient, SE = standard error
z = 0.99
the chances (odds) is 68% that the true score is located within the interval (lower precision, lower CI)
z = 1.96
the odds are 95% that the true score located within the interval (medium precision, medium CI)
z = 2.58
the odds are 99% that the true score located within the interval (higher precision, higher CI)
Confidence intervals indicate…
the limits within which a certain possible score may be
assumed to be true
Standard error (SE)
Standard deviation of raw scores around true scores (SD of measurement errors)
SE formula
SE = σ * √(1 - rxx)
The higher rxx
the lower SE
The lower σ
the lower SE
Test-retest
A specific test is used multiple times or at least two times (coefficients between these tests)
Parallel (or alternative) versions
Coefficients between the different versions
Internal consistency measures (split-half, Cronbach’s alpha, KR-20)
Test used one time! KR-20 is for dichotomous items (only two options)