Psychology is an empirical science. This mini-lesson covers quantitative and qualitative methods, experiments, correlational studies, sampling, ethics, and the credibility and bias of research — the toolkit you use to evaluate every study in the course.
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Research · overview
Quantitative and qualitative research
Quantitative research produces numerical data (e.g. reaction times, scores) and tests hypotheses statistically — e.g. Loftus and Palmer.
Qualitative research produces rich, descriptive data (words, meanings) from interviews, observations and case studies — e.g. Bartlett's recall protocols.
A study starts with an aim and, for experiments, a testable hypothesis.
Experiments
The experimental method
An experiment manipulates an independent variable (IV) and measures its effect on a dependent variable (DV), while controlling other variables. Only a controlled experiment can establish cause and effect.
Laboratory experiment — high control (e.g. Loftus and Palmer).
Field experiment — natural setting, more realism, less control.
Natural/quasi experiment — the IV is pre-existing, not manipulated.
Confounding variables are uncontrolled variables that offer an alternative explanation — the enemy of a valid experiment.
Quick check
Which is right?
?What feature of a well-controlled experiment allows it to establish cause and effect?
Experimental design
Experimental designs
Independent measures — different participants in each condition (no order effects, but participant variables differ).
Repeated measures — same participants in every condition (controls participant variables, but risks order effects).
Matched pairs — different but matched participants.
Counterbalancing (e.g. half do condition A first, half B first) controls order effects in a repeated-measures design.
Quick check
Which is right?
?A repeated-measures design is especially vulnerable to which problem?
Correlational studies
Correlational studies
A correlational study measures the relationship between two co-variables without manipulating anything. Correlations can be positive, negative or zero.
Golden rule:correlation does not equal causation. A third (confounding) variable may explain the link, or the causal direction may be reversed. Maguire's taxi-driver finding is correlational for this reason.
Quick check
Which is right?
?What can a correlational study NOT establish?
Sampling
Sampling techniques
Random sample — every member of the target population has an equal chance of selection (most representative).
Opportunity sample — whoever is available (convenient but biased).
Self-selected (volunteer) — people respond to an advert.
Stratified — subgroups represented in proportion.
Good sampling improves generalisability; a biased sample limits it.
Quick check
Which is right?
?Which sampling method gives every member of the target population an equal chance of selection?
Ethics
Research ethics
Studies with human participants must respect key ethical principles:
Informed consent and the right to withdraw.
Protection from harm (physical and psychological).
Confidentiality / anonymity.
If deception is unavoidable, participants must be fully debriefed afterwards.
Classic studies (e.g. Bandura's Bobo doll, Milgram's obedience research) are still debated on ethical grounds.
Quick check
Which is right?
?If a study used deception, what must researchers always do afterwards?
Credibility & bias
Credibility, bias and generalisability
Internal validity — did the study really measure what it claims (free of confounds)?
External validity — do the findings generalise to other people, settings and times?
Reliability — would the study give consistent results if repeated?
Watch for researcher bias and demand characteristics (participants guessing the aim).
Sort it
Sort each statement to its method
Tap a statement, then tap the research method it describes.
🧪 Experiment
📈 Correlation
👥 Sampling & ethics
Match it
Match each term to its definition
Tap a term on the left, then its definition on the right.
Term
Definition
Recap
The big ideas to know
Methods: quantitative (numbers) vs qualitative (words/meaning)
Experiments: manipulate IV, control confounds → cause and effect; lab/field/natural