Experimental Method

INDEPENDENT VARIABLE (IV)

A manipulated variable in an experiment or a study whose presence or degree determines the change in the dependent variable.

DEPENDENT VARIABLE (DV)

Measures of the behavior used by the researcher to assess the effect (if any) of the independent variables.

BETWEEN SUBJECTS/GROUPS DESIGN

Independent Group Design

Each separate group in the experiment represents a different condition as defined by the level of the Independent Variable (IV).

Randomly assign subjects to group condition.

Seeks to establish equivalent groups at start of experiment.

IV is the only difference between groups.

Try to minimize nuisance factors; for example: different experimenters, different rooms, different time of day, etc.

WITHIN – SUBJECTS DESIGN

Dependent Group Design

This is a design in which the IV is implemented by administering all the levels of the IV to each subject. In other words, all subjects receive all treatments.

Balance for “practice effects” by random assignment to treatment.

Subjects can serve as their own control.

This test is more powerful than Independent groups test because subjects are in both conditions which results is reduced VARIANCE between the two conditions.

COMPLEX DESIGN

A design in which 2 or more IV are studied simultaneously.