Defining and Measuring Variables

Forming a Hypothesis  Tentative question that makes a prediction  Must be measurable  Operationally defining variables  Variables: anything that can have more than two characteristics  Examples: IQ score, weight, driving violations, BAC

Operational Definition  Procedure for measuring and defining a construct  Specific procedure for measuring an external, observable behavior  Uses the resulting measurement as a definition Eating pop tarts increases memory. Memory  # of items recalled correctly on a test

Important When Defining Constructs  Validity-measures what it is supposed to measure  Reliability-stability or consistency of the measurement

Ways to increase validity and reliability  Physiological measures  MRI  EEG  EKG  Behavioral measures  Tests  Ratings  Reaction times

Problems  Artifacts: other variable that influences or distorts measurement  Experimenter bias: research influences participants or measurement  Single-blind  researcher doesn’t know result  Double-blind  research and participant don’t know result  Reactivity-participants modify their natural behavior because they know they are being observed