AP Psychology – Research Methods (Experimental, Correlational, Case Study, Survey)

AP Psychology – Research Methods (Experimental, Correlational, Case Study, Survey)

AP Psychology: Research Methods Study Guide

(Experimental, Correlational, Case Study, Survey)

What This Is

Research methods are the tools psychologists use to study behavior and mental processes. On the AP exam, you’ll need to compare methods, identify strengths/weaknesses, and interpret data—especially in FRQs. For example, Stanley Milgram’s obedience study (1963) used an experiment to test how far people would go in obeying an authority figure (shocking a "learner" for wrong answers). This study revealed dark truths about human behavior but also raised ethical concerns (deception, psychological harm), showing why method choice matters.

Key Terms & Concepts

• Hypothesis: A testable prediction about the relationship between variables (e.g., "Caffeine improves memory recall").
• Independent Variable (IV): The factor manipulated by the researcher (e.g., caffeine dose).
• Dependent Variable (DV): The measured outcome (e.g., memory test scores).
• Operational Definition: A clear, precise description of how a variable is measured (e.g., "Memory recall = number of words correctly remembered from a 20-item list").
• Experimental Group: Participants exposed to the IV (e.g., group given caffeine).
• Control Group: Participants not exposed to the IV (e.g., group given a placebo).
• Random Assignment: Assigning participants to groups by chance to minimize bias (e.g., flipping a coin).
• Confounding Variable: An uncontrolled factor that could skew results (e.g., participants’ prior caffeine tolerance).
• Correlation: A statistical relationship between two variables (e.g., "Ice cream sales and drowning rates both rise in summer").
• Correlation Coefficient (r): A number between -1 and +1 showing strength/direction of a relationship.
  • +1 = perfect positive correlation (both variables increase together).
  • -1 = perfect negative correlation (one increases, the other decreases).
  • 0 = no correlation.
• Case Study: An in-depth analysis of one individual or group (e.g., Phineas Gage, whose brain injury revealed links between frontal lobes and personality).
• Survey: A self-report method gathering data from many people (e.g., "How often do you feel stressed?").
• Wording Effects: How phrasing influences responses (e.g., "Do you support killing babies?" vs. "Do you support women’s reproductive rights?").
• Naturalistic Observation: Watching behavior in real-world settings without interference (e.g., Jane Goodall studying chimpanzees).
• Placebo Effect: When participants’ expectations (not the IV) cause a change (e.g., feeling less pain after taking a sugar pill).
• Double-Blind Procedure: Neither participants nor researchers know who’s in the experimental/control group (reduces bias).

Step-by-Step: How to Analyze a Research Scenario

Use this for FRQs or multiple-choice questions about research methods.

1. Identify the Method

2. Is it an experiment (IV/DV, random assignment), correlational study (no manipulation, just observation), case study (one person/group), or survey (self-report)?

3. Spot the Variables

4. Experiment: What’s the IV (manipulated) and DV (measured)?

5. Correlation: What two variables are being compared?

6. Check for Bias/Confounds

7. Experiment: Was there random assignment? A control group? Placebo?

8. Survey: Were questions worded neutrally? Was the sample representative?

9. Evaluate Strengths/Weaknesses

10. Experiment: High control (), but artificial setting (?).
11. Correlation: Shows relationships (), but cannot prove causation (?).
12. Case Study: Rich detail (), but not generalizable (?).

13. Survey: Quick data collection (), but self-report bias (?).

14. Draw Conclusions

15. Can you infer causation (only experiments with random assignment)?
16. Are the results generalizable (large, diverse sample)?

Common Mistakes

• Mistake: Assuming correlation = causation.

• Correction: Correlation shows a relationship, but only experiments (with random assignment) can prove causation. Example: "Ice cream sales and drowning rates both rise in summer"-Third variable (heat) causes both.

• Mistake: Forgetting operational definitions.

• Correction: Always ask: "How was this measured?" Example: "Aggression" could mean verbal insults, physical fights, or self-reported anger.

• Mistake: Ignoring confounding variables.

• Correction: Look for alternative explanations. Example: A study finds "students who sleep more get better grades"-Confound: Students who sleep more might also study more.

• Mistake: Overgeneralizing case studies.

• Correction: Case studies (e.g., Phineas Gage) provide deep insights but can’t be applied to everyone.

• Mistake: Misinterpreting correlation coefficients.

• Correction: A strong correlation (e.g., r = -0.8) is not weaker than r = +0.8—sign only shows direction, not strength.

AP Exam Insights

1. FRQs Love Research Methods

2. You’ll often get an FRQ asking you to design an experiment or evaluate a study’s flaws. Example:

   • "A researcher wants to test if listening to music improves test scores. Describe how they could conduct an experiment, identifying the IV, DV, and potential confounds."

3. Correlation-Causation is a Favorite Trap

4. Multiple-choice questions will trick you with statements like "A study found that people who meditate are happier. Therefore, meditation causes happiness."-No! Could be reverse causation (happy people meditate more) or a third variable (e.g., income).

5. Ethics Matter

6. Know APA ethical guidelines: Informed consent, debriefing, protection from harm, confidentiality. Example: Milgram’s study violated protection from harm (psychological distress).

7. Wording Effects in Surveys

8. Example: "Do you support the murder of unborn children?" vs. "Do you support a woman’s right to choose?"-Same topic, different responses.

Quick Check Questions

1. A researcher finds that students who sleep more have higher GPAs. What can the researcher conclude? a) Sleeping more causes higher GPAs. b) Higher GPAs cause students to sleep more. c) There is a correlation between sleep and GPA, but causation cannot be determined. d) Sleep and GPA are unrelated. Answer: C-Correlation does not prove causation (could be a third variable, like study habits).

2. In an experiment testing if caffeine improves memory, what is the IV? a) Memory test scores b) Caffeine dose c) Participants’ age d) Time of day Answer: B-The IV is the manipulated variable (caffeine).

3. Short FRQ: A psychologist wants to study the effects of social media on anxiety. Describe how they could use a correlational study and an experiment to investigate this. Identify one strength and one weakness of each method. Sample Answer:

4. Correlational Study: Survey participants on social media use and anxiety levels, then calculate a correlation coefficient.
   • Strength: Can study real-world behavior without manipulation.
   • Weakness: Cannot prove causation (e.g., anxious people might use social media more).
5. Experiment: Randomly assign participants to high vs. low social media use for a week, then measure anxiety.
   • Strength: Can infer causation (if random assignment is used).
   • Weakness: Artificial setting may not reflect real-world behavior.

Last-Minute Cram Sheet

1. Experiment: IV (manipulated), DV (measured), random assignment = causation.
2. Correlation: r = -1 to +1, no causation ( third variables!).
3. Case Study: Phineas Gage (brain injury-personality change), not generalizable.
4. Survey: Wording effects matter (e.g., "murder" vs. "right to choose").
5. Naturalistic Observation: Jane Goodall (chimps), no interference.
6. Placebo Effect: Expectations cause change (e.g., sugar pill-pain relief).
7. Double-Blind: Neither participants nor researchers know groups ( reduces bias).
8. Confounding Variable: Uncontrolled factor (e.g., caffeine study-prior sleep).
9. Operational Definition: How a variable is measured (e.g., "aggression = number of punches").
10. Ethics: Informed consent, debriefing, no harm ( Milgram’s study violated this).

AP Trap: "This study proves X causes Y"-Only experiments with random assignment can prove causation!