AP Psychology · Unit 0

AP Psychology Unit 0: Science Practices & Research Methods

Unit 0 is the toolkit the rest of the course is built with: how psychologists design studies, what counts as evidence, and how to read results. It never gets its own exam section because it's in every section — most visibly the AAQ, which is one long research-methods question.

The 5 Research Methods in AP Psychology

Every research methods question starts with one decision: which method was used? Know all five, and know each one's superpower and blind spot.

• Experiment — the researcher manipulates a variable and randomly assigns participants. The only method that can show cause and effect.
• Correlational study — measures how two variables move together. Shows relationships and enables prediction, but correlation does not prove causation (the third-variable problem).
• Case study — one person or small group in depth. Rich detail, famous patients (like H.M.), but results may not generalize.
• Naturalistic observation — watching behavior in its real setting without interfering. High realism, no control.
• Survey — self-reported data from many people fast. Efficient, but vulnerable to wording effects and social desirability bias, and it needs a random sample to generalize.

Also know meta-analysis — a statistical combination of many studies' results — because the redesigned exam loves to hand you one in the AAQ.

Variables, Groups, and Experimental Design

For any experiment, be able to label the independent variable (what's manipulated), the dependent variable (what's measured), and confounding variables (anything else that could explain the result). Participants are split by random assignment into the experimental group and the control group, which may get a placebo. Control for expectations with single-blind and double-blind procedures, and define fuzzy concepts with operational definitions so the study can be replicated. Sampling matters too: a random sample lets you generalize to the population; a representative sample mirrors its makeup.

Ethical Guidelines in AP Psychology

The ethical guidelines show up on the exam every year, usually as "what did this study do wrong?" Know these six: informed consent (and assent plus guardian permission for minors), protection from harm, confidentiality, deception only when justified, debriefing afterward, and approval by an Institutional Review Board (IRB) — or IACUC for animal research. If a scenario skips one of these, that's your answer.

Statistics You Need for Unit 0

You don't need heavy math — you need to read numbers the way a researcher does. That means the measures of central tendency (mean, median, mode) and when a skewed distribution makes the median more honest than the mean; range and standard deviation for spread; the normal curve; and percentile rank. For relationships, read a correlation coefficient from −1 to +1 (sign = direction, size = strength) and a scatterplot. Finally, statistical significance (p < .05) means a result is unlikely to be chance — and effect size tells you whether it's big enough to matter.

How to Study Unit 0

Don't study research methods in AP Psychology as vocabulary — study them as decisions. For every study you meet in Units 1–5, ask: what method is this, what were the variables, and what can it not conclude? The experiments on this site are working examples — run the Stroop test and identify its IV, DV, and design for yourself. Then drill the skill where it pays: the AAQ guide, the practice test, and the units overview.

AP Psychology Unit 0 — FAQ

What is Unit 0 in AP Psychology?

Unit 0 covers the science practices of the redesigned course: research methods, experimental design, variables, ethical guidelines, and basic statistics. It isn't tested as a standalone unit — its skills are woven through every multiple-choice section and both free-response questions, especially the AAQ.

What are the 5 research methods in AP Psychology?

The experiment (the only method that shows cause and effect), the correlational study, the case study, naturalistic observation, and the survey. Meta-analysis, which combines results across many studies, also appears on the exam.

Is Unit 0 on the AP Psychology exam?

Yes — everywhere. Research-methods questions appear throughout the multiple-choice section, and the AAQ free-response question is entirely about reading a study and analyzing its method, variables, and conclusions. Unit 0 skills are the highest-leverage content on the exam.

What are the ethical guidelines in AP Psychology?

Know informed consent and informed assent for minors, protection from harm, confidentiality, limited and justified use of deception with debriefing afterward, and IRB approval for human research and IACUC approval for animal research.

See the Methods in Action

Every experiment on this site is a live research-methods example. Run one, then label its design yourself.

Run an Experiment

Aligned to the College Board's redesigned AP Psychology course (2024–25). AppsychologyLab is not affiliated with the College Board.