Experimental Research Strategy

Experiment Establish existence of a cause-and-effect relationship between two variables Demonstrating that changes in one variable are directly responsible for changes in another variable Ex: children’s weight and math skills

Experimental Study Four basic elements – Manipulation: manipulates one variable by changing its value to create a set of two or more treatment conditions – Measurement: obtain scores from each treatment – Comparison: compare scores from each trt – Control: all other variables controlled so they don’t influence the two variables being examined

Cialdini, Reno, & Kallgren (1990) Purpose: Examine perceived social norms affect people’s littering beh Methods: Condition 1  clean floor Condition 2  dirty floor Posted flyer on window: measured whether driver littered Results: More litter in already-littered environ

Important Terms Independent variable – Levels, groups, treatments, conditions Dependent variable – Observed for changes to assess effects of manipulating IV

Elements of an Experiment Manipulation-identifying specific values of IV and then creating conditions; purpose is to identify direction of a relationship Control-eliminate confounds (matching, counterbalancing, control groups, randomization) – Confounds Influence DV Must vary systematically with IV

Groups Experimental – Receives IV Control – No-treatment Purpose to provide a standard of normal behavior “baseline” against which the treatment condition can be measured Placebo – To ensure no response due to belief medicine effective