Experimental Research

Independent variable

• Dependent variable

• Causation

CHAPTER 7

Experimental Research

Establishing causation

• Universal laws

• Statistical laws

Requirements for causal relationship

• IV must precede the DV

• IV and DV must covary

• Changes in DV must be result of changes in the IV

• Control – a researcher attempts to exclude other possible causes of the effect he/she is studying

Exposing participants to the IV

• Conditions

• Treatment

• Attribute variables

• Selection

• equivalence

• Random assignment

increases the internal validity of a study while random sampling increases external validity of a study

Controlling for the effects of extraneous influences

• Threshold effects

• Experimenter effects

• Other effects

Experimental Research Designs

• Full experiment

• Quasi-experiment

• Preexepriment

Factorial design

• Studies with more that 1 IV are summarized with a design statement

• Example a 2 x2 design

• Between-group design

Within-group design

• Lab versus field experiments