Lecture 7 Psyc 300A

Measurement Operational definitions should accurately reflect underlying variables and constructs When scores are influenced by other things, we have measurement error Measurement error may include: –Trait error –Method error

Reliability Reliabilty = True score/(true score + error) Refers to stability of a measure: Is it repeatable? Types (all use correlation coefficient) –Test-retest –Alternate forms –Internal consistency –Interrater

Validity Extent to which a procedure measures what it is supposed to measure Types of Validity (measurement) Criterion validity –Extent to which scores predict some current or future situation –Predictive: future event –Concurrent: current event Content

Validity (continued) Types of Validity Construct validity –Extent to which scores reflect hypothetical construct –Convergent: Extent to which two different measures of the same thing are consistent –Divergent: Extent to which two different measures of different things are different from one another