AP PSYCH Research Methods

Experiment

The researcher manipulates an independent variable to determine its effect on a dependent variable; the only method that shows cause and effect

Independent Variable (IV)

The variable that is manipulated or changed by the researcher

Dependent Variable (DV)

The variable that is measured in an experiment; it changes depending on the IV

Control Groups

The group that does NOT receive the experimental treatment and is used for comparison

Experimental Group

The group that receives the treatment or manipulation of the independent variable

Random Assignment

Assigning participants to groups in an experiment by chance to reduce bias and ensure groups are similar

Random Sample

A sample in which every member of the population has an equal chance of being selected

Correlational Study

A research method that measures the relationship between two variables without manipulating them

Correlation Coefficient ( r )

A number from a -1 to +1 that shows the strength and direction of a relationship between two variables

Positive Correlation

A relationship where both variables increase or decrease together

Negative Correlation

A relationship where one variable increases while the other decreases

Zero Correlation

No relationship between two variables

Survey Method

A research method that collects data by asking people questions

Naturalistic Observation

Observing behavior in a natural environment without interference or manipulation

Case Study

An in-depth study of one person or small group

Longitudinal Study

Follows the same participants over a long period, which is time-consuming but effective for tracking developmental changes

Cross-Sectional Study

Compares different groups of people at one time, offering a faster alternative to longitudinal studies but confounding results with cohort effects

Double-Blind Study

A study where neither the participants nor the researchers know who is in the control or experimental group, preventing bias

Selection Bias

A flaw in sampling where participants are not representative of the population

Response Bias

When participants do not answer questions truthfully or accurately

Social Desirability Bias

When people answer questions in a way that makes them look good rather than being honest

Experimenter Bias

When the researchers expectations influence the outcome of the study

Placebo Effect

When participants experience a change because they believe they received a treatment, not because of the treatment itself

Confounding Variable

An outside factor that affects both the IV and DV, potentially ruining the results

Validity

The extent to which a test or study measures what it is supposed to measure

Reliability

The consistency of a test or measurement over time

Mean

The average of a set of numbers

Median

The middle value in a set of numbers

Mode

The most frequently occurring value in a set of numbers

Standard Deviation

A measure of how spread out data values are from the mean

Informed Consent

Participants must be told what the study is about and agree to participate

Confidentiality

Keeping participants personal data private

Debriefing

Explaining the purpose of the study to participants after it is completed

Harm Principle

Researchers must avoid causing physical or psychological harm to participants

Cause and Effect

A conclusion that one variable directly influences another, only possible in EXPERIMENTS

Correlation does NOT imply Causation

A relationship between two variables does not mean one causes the other

Operational Definition

A precise definition of how a variable is measured or manipulated in a study

Bias

Any factor that unfairly influences research results

Generalization

The extent to which results can apply to a larger population