Difficulty: Introductory | Prerequisites: None
Research methods is the toolbox for every other topic in psychology. This unit covers how psychologists design studies, control for bias, measure variables, and draw conclusions. You will see these concepts woven into exam questions across all units, and there is always a dedicated block of questions on experimental design, variable identification, and the difference between correlation and causation. Knowing the vocabulary here is non-negotiable for the final.
Science depends on objectivity, systematic observation, and repeatable data. Psychologists use experiments, naturalistic observation, case studies, surveys, and correlational designs to study behaviour. Understanding the difference between independent and dependent variables, control and experimental groups, reliability and validity, and correlation and causation will carry you through a large chunk of the exam.
Hypothesis
A specific, testable prediction about the relationship between variables. Martha thinks cats prefer Brand A over Brand B, so she develops a hypothesis and creates an experiment.
In simple terms, it is your educated guess that you can test.
Theory
A broad explanation of observed phenomena, supported by a body of evidence. Theories are not guesses; they are well-supported frameworks.
Replication
Repeating a study to see whether the same results occur. When Martha's results differ from other scientists', her experiment undergoes replication to confirm the findings.
In simple terms, can someone else do the same thing and get the same answer?
Peer review
The process by which other scientists evaluate a study's methods and conclusions before publication. This is different from replication: peer review evaluates the study, replication re-runs it.
Independent variable (IV)
The variable the researcher manipulates. In a sleep study with different light conditions (natural light, fluorescent light, no light), the type of light is the independent variable.
Dependent variable (DV)
The variable the researcher measures, the outcome. In the sleep study, the time taken to wake from deep sleep would be the dependent variable.
Control variable / control condition
The baseline condition against which experimental conditions are compared. "No light" in the sleep study serves as the control.
Confounding variable
An uncontrolled variable that may influence the dependent variable, making it difficult to determine the true effect of the independent variable.
Random assignment
Assigning participants to groups by chance (e.g. picking names from a hat) to ensure groups are equivalent before the experiment begins.
Naturalistic observation
A descriptive research method in which behaviour is observed in its natural setting without interference. Nate watching gamblers at a casino poker table on Saturday nights is naturalistic observation.
Case study
An in-depth study of a single individual or small group.
Correlation
A measure of the relationship between two variables. Correlation does not imply causation. "High temperature is related to lower activity in children" is a correlation, not a causal claim.
Cross-sectional study
A study that compares different age groups at a single point in time. Katie testing 3-to-5-year-olds alongside 15-to-18-year-olds on aggression is using a cross-sectional design.
Longitudinal study
A study that follows the same group of people over an extended period.
Reliability
The consistency of a measurement. Julie's home scale reads 172.4 pounds every day for two weeks: that is reliable, because the result is consistent.
Validity
The accuracy of a measurement, whether it measures what it claims to measure. Julie's scale consistently reads 172.4, but the doctor's scale (assumed accurate) reads 168.3. Julie's scale is reliable but not valid.
In simple terms, reliability is about consistency; validity is about accuracy.
Generalization
Applying the results from a sample to a larger population. Patrick taking results from 500 OSU students and applying them to all college students is making a generalization.
Critical thinking
Evaluating evidence, considering alternatives, and basing conclusions on reasoning rather than gut feelings or assumptions. Julio accepting peer criticism and revising his ideas is the best example.
Science relies on observable, repeatable data (true).
Science uses systematic observation (true).
Science relies on subjectivity (false, this is the correct answer when asked "which is false?").
Naturalistic observation: watching behaviour in a natural setting without intervening (e.g. observing gamblers at a casino).
Case study: deep dive into a single individual or event.
Correlation: measuring the relationship between two variables. Does not allow causal conclusions.
Experiment: the only method that can establish cause and effect, because the researcher manipulates the IV and controls other variables.
IV = what the researcher changes (the light conditions).
DV = what the researcher measures (wake-up time).
Control = the baseline condition (no light).
Random assignment ensures groups start equivalent (picking names from a hat).
A measurement can be reliable without being valid (consistently wrong).
A measurement cannot be valid without first being reliable.
Julie's scale: reliable (same reading every day) but not valid (differs from the accurate reading at the doctor's office).
John's scale: reads the same thing every day, doctor's scale reads differently = reliable but not valid.
Martha develops a hypothesis (specific, testable prediction), not a theory.
When results disagree with other scientists', the experiment undergoes replication, not peer revision.
Cross-sectional: compares different age groups at one point in time (Katie's study).
Longitudinal: follows the same people over time.
Mixed longitudinal: combines elements of both.
Students confuse hypothesis with theory. A hypothesis is a specific testable prediction. A theory is a broad, well-supported explanation.
Students confuse replication with peer review. Replication re-runs the study. Peer review evaluates the study's quality before publication.
"Reliable" does not mean "correct." A scale that consistently gives the wrong weight is reliable but not valid.
Correlation does not mean causation. High temperature being associated with lower activity in children tells you nothing about whether one causes the other.
⚠️ "Science relies on subjectivity" is FALSE. This appears at least twice.
⚠️ Know the hypothesis → replication pairing for the Martha question (not theory, not peer revision).
⚠️ Naturalistic observation = observing in a natural setting (casino, classroom). The Nate/gambler question appears twice.
⚠️ No light = control variable in the sleep study question. This also appears twice.
⚠️ Cross-sectional = different age groups at one time point. Katie's study design appears twice.
⚠️ Julie/John's scale = reliable but not valid. This concept appears in multiple forms.
⚠️ Critical thinking = accepting criticism, evaluating evidence. Not "gut feelings" or ignoring others' ideas.
⚠️ Generalization = applying sample results to a larger population. Patrick's question appears twice.
True or False: Science relies on subjectivity. False. Science relies on objectivity and repeatable data.
Fill in the blank: A scale that gives the same reading every time but is 4 pounds off from the true weight is __________ but not __________. Reliable, valid.
True or False: Correlation between two variables means one causes the other. False. Correlation does not imply causation.
Fill in the blank: A study comparing 5-year-olds and 15-year-olds at the same point in time is a __________ study. Cross-sectional.
Fill in the blank: The variable a researcher manipulates is called the __________ variable. Independent.
Q: Martha thinks cats prefer Brand A. She develops a _____ and when her results differ from others', the experiment undergoes _____ to confirm the findings.
A: Hypothesis; replication. She develops a specific, testable prediction (hypothesis), and the study is repeated (replication) to check whether the results hold.
Q: Nate watches gamblers' body language at a casino on Saturday nights. What method is he using?
A: Naturalistic observation. He is observing behaviour in its natural setting without interfering.
Q: A researcher assigns participants to groups by picking names out of a hat. What is this?
A: Random assignment. It ensures each participant has an equal chance of being in any group.
Q: Julie's home scale reads 172.4 every day but the doctor's scale reads 168.3. What describes Julie's scale?
A: Reliable but not valid. It is consistent (reliable) but inaccurate (not valid).
Variable identification comes back in every unit that discusses research findings: the sleep study in the Consciousness unit, aggression studies in the Development unit, and stress experiments in the Health Psychology unit.
Reliability and validity connect to the Intelligence unit, where IQ tests must demonstrate both properties.
Understanding correlation vs. causation is essential for evaluating claims in the Social Psychology and Personality units.
research methods, scientific method, hypothesis, theory, replication, peer review, independent variable, dependent variable, control variable, confounding variable, random assignment, naturalistic observation, case study, correlation, experiment, cross-sectional study, longitudinal study, reliability, validity, generalization, critical thinking, PSYCH 1100, general psychology, Ohio State