AP Psychology Methods and Approaches

Experiment

An investigation seeking to understand relations of cause and effect. The experimenter changes a variable (cause) and measures how it changes another variable (effect).

Independent Variable

The manipulated variable in an experiment.

Dependent Variable

What is measured in an experient.

Control Variable

Remains unchanged throughout the experiment.

Population

The group of interest in an experiment.

Representative Sample

Subset of population in an experiment that mirrors the characteristics of the larger group.

Representativeness

The degree to which a sample reflects the diverse characteristics of the population that is being studied.

Random Sampling

Randomly selecting people of a sample of a population to ensure maximum representativeness.

Bias of Selection

Occurs when people are selected in a physical space.

Self-selection Bias

Occurs when the people being studied have some control over whether or not to participate.

Pre-screening/Advertising Bias

Occurs often in medical research; how volunteers are screened or where advertising is placed might skew the sample.

Healthy User Bias

Occurs when the study population tends to be in better shape than the general population.

Single-blind Design

The subjects in an experiment do not know whether they are in the control or experimental group.

Double-blind Design

Neither the subjects nor the researchers in an experiment who is in the two groups.

Correlational Research