Experiments Testing cause-effect relationship between two variables Changed by observer (all other independent variables should remain constant - not more than one changed at the same time) Goal: Test whether it has an influence Independent Variable Presence/absence of binders on Hans Dependent Variable Percentage of correct answers Within-Subject Experiment Only one subject (Hans) tested repeatedly Changing of one independent variable (others constant) Between-Groups Experiment Manipulation of independent variable (different treatments) applied to different groups of subjects Usually random assignment: participants are randomly picked to avoid influencing results (bias) - still influence of chance Hypothesis: both drug & psychotherapy help reduce depression & work best in combination