psychometrics Flashcards
what is psychometrics
branch of psychology concerned with the scientific measurement of individual differences
how are psychometrics used in clinical paychology
- interviews to assess patients
- usually lots of tests rather than a single test
- diagnosis of mental illnesses, learning disabilities
how are psychometrics used in forensic psychology
*used to inform legal decision making
deciding whether a defendant is legally competent
*levels of intelligence vis IQ testing
how are psychometrics used in educational and occupational psychology
*measurement of academic abilities
reliability
the consistency of a measure across time and circumstances
validity
does the measure asses what it claims to?
internal reliability
how well all of the items in a scale measure the construct
split half reliability (internal reliability)
pearsons r for two halves of the scale
odd-even reliability (internal reliability)
correlate odd and even sets of scores
alpha reliability - Cronbachs alpha (internal reliability)
average of very possible half correlated with average of every other possible half (use SPSS)
test-retest reliability
correlate scores at T1 with T2
why is alternate form reliability used
to cancel out memory effects
face validity
informal assessment of whether the content of a scale appears to measure what it sets out to
content validity
systematic examination of the extent to which test covers a representative sample of the domain to be measured
concurrent validity
does the scale correlate well with other measures of the same concept taken at the same time
predictive validity
extent to which a measure predicts something that it theoretically should be able to predict
conceptual variable (scale construct)
the idea that we are attempting to capture - hypothetical constructs that cant be directly observed
*eg quality of lifr
operational variable (scale construct)
the specific way in which the variable of interest is measured in the study
nominal level (level of scale)
the variable takes response values with no intrinsic ranking eg gender
ordinal level (level of scale)
the variable takes response values with some intrinsic ranking eg life satisfaction scale (satisfied, somewhat satisfied)
scale level (level of scale)
the variable takes ranked response values with constant differences eg life satisfaction scale (ranging from 1-10)
