AP Psychology Research Methods & Statistics Key Concepts

Hindsight Bias

The tendency to believe, after learning an outcome, that one would have foreseen it; also known as the 'I-knew-it-all-along' phenomenon.

Critical Thinking

The process of actively and skillfully analyzing, synthesizing, and evaluating information to reach well-reasoned conclusions.

Peer Reviewers

Independent experts who evaluate research manuscripts before publication to ensure quality, accuracy, and adherence to scientific standards.

Theory

An explanation using integrated principles that organizes observations and predicts behaviors or events.

Hypothesis

A testable prediction, often implied by a theory, about what will happen under specific conditions.

Falsifiable

The principle that a scientific hypothesis or theory must be capable of being proven false through empirical testing.

Operational Definition

A precise statement of how a variable is measured or manipulated in a particular study.

Replication

The process of repeating a research study to see whether the basic findings can be reproduced.

Case Study

An in-depth investigation of a single individual, group, or event to understand complex phenomena.

Naturalistic Observation

Observing and recording behavior in naturally occurring situations without trying to manipulate or control the situation.

Survey

A research method that uses questionnaires or interviews to collect self-reported data from participants.

Social Desirability Bias

The tendency for participants to respond in ways they believe are socially acceptable rather than truthfully.

Self-Report Bias

The tendency for individuals to inaccurately report their own behaviors, thoughts, or feelings due to various factors like memory limitations or desire to appear favorable.

Population

The entire group of individuals about which researchers want to draw conclusions.

Sample Bias

A systematic error that occurs when the sample is not representative of the target population.

Random Sample

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

Variable

Any factor that can vary or change in an experiment or research study.

Correlation

A statistical measure that indicates the extent to which two variables are related or change together.

Regression Toward the Mean

The tendency for extreme measurements to be closer to the average when measured again.

Correlation Coefficient

A statistical measure (ranging from -1 to +1) that indicates the strength and direction of a linear relationship between two variables.

Scatterplot

A graph showing the relationship between two variables, with each point representing an individual's scores on both variables.

Illusory Correlation

The perception of a relationship between two variables when no such relationship exists.

Experiment

A research method in which an investigator manipulates one or more variables to observe their effect on some behavior or mental process.

Random Assignment

The process of assigning participants to experimental and control groups by chance, minimizing pre-existing differences between groups.

Single-Blind Procedure

An experimental procedure in which participants don't know whether they're in the experimental or control group.

Double-Blind Procedure

An experimental procedure in which neither participants nor researchers know who is in the experimental or control group.

Placebo Effect

The phenomenon where participants experience changes simply because they believe they are receiving treatment.

Experimental Group

The group in an experiment that receives the treatment or manipulation being studied.

Control Group

The group in an experiment that does not receive the treatment, serving as a comparison for the experimental group.

Independent Variable (IV)

The variable that is manipulated by the experimenter to observe its effect on the dependent variable.

Confounding Variable

An unwanted variable that influences the dependent variable and makes it difficult to determine causation.

Dependent Variable (DV)

The variable that is measured in an experiment; the outcome variable that may be affected by the independent variable.

Experimenter Bias

The tendency for researchers to unconsciously influence the results of their study in the direction of their expectations.

Validity

The extent to which a test or study measures what it claims to measure.

Qualitative Research

Research that focuses on collecting and analyzing non-numerical data to understand concepts, opinions, or experiences.

Quantitative Research

Research that focuses on collecting and analyzing numerical data to identify patterns, test hypotheses, and make predictions.

Descriptive Statistics

Numerical measures that describe and summarize data from a sample or population.

Inferential Statistics

Statistical methods used to make inferences about a population based on data from a sample.

Histogram

A bar graph that shows the frequency distribution of a dataset.

Mode

The most frequently occurring score in a distribution.

Mean

The arithmetic average of all scores in a distribution.

Median

The middle score in a distribution when scores are arranged from lowest to highest.

Percentile Rank

The percentage of scores in a distribution that fall below a particular score.

Range

The difference between the highest and lowest scores in a distribution.

Standard Deviation

A measure of how spread out scores are from the mean in a distribution.

Normal Curve

A symmetrical, bell-shaped frequency distribution where most scores cluster around the mean.

Skewed Distribution

An asymmetrical distribution where scores cluster toward one end, creating a 'tail' on the other side.

Meta-Analysis

A statistical technique that combines results from multiple studies to identify overall patterns and effects.

Statistical Significance

The likelihood that research findings are due to something other than chance, typically set at p < 0.05.

Effect Size

A statistical measure of the strength of the relationship between variables or the magnitude of a treatment effect.

Informed Consent

The process of informing potential participants about the nature, risks, and benefits of research before they agree to participate.

Debriefing

The process of explaining the true purpose and procedures of a study to participants after their participation is complete.