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IB DP Psychology — Concepts | SL & HL | Paper 1, 2 & 3
🎯 Learning Intentions By the end of this note, you will be able to:
- Define operationalization, variables (independent, dependent, extraneous, confounding), and hypothesis using IB-aligned terminology.
- Explain why operationalization is essential for conducting valid and replicable psychological research.
- Describe the key features of experimental, correlational, observational, and self-report research methods used in psychology.
- Distinguish between quantitative and qualitative data and explain when each is appropriate.
- Evaluate the strengths and limitations of different research methods using the concept areas of Measurement, Causality, and Bias.
- Apply knowledge of research methods and operationalization to a real-world case study scenario.
- Analyse research designs using relevant concept areas: Measurement, Causality, Bias, and Responsibility.
Introduction & Context
Imagine you want to find out whether listening to music while studying improves academic performance. You have a hunch — perhaps from personal experience — that it does. But how would you actually test this? What exactly counts as "listening to music"? What counts as "improved performance"? And how would you know whether any change you observe was caused by the music, or by something else entirely — like the fact that students who choose to listen to music are simply more motivated in the first place?
These are not trivial questions. They sit at the heart of psychological research. Psychology aims to understand human behaviour and mental processes in a systematic, evidence-based way. But to do that, researchers must make abstract ideas — like "stress," "memory," "aggression," or "well-being" — concrete enough to measure. They must also choose methods that are appropriate for the question they are asking. The choices researchers make at this stage shape everything that follows: the data they collect, the conclusions they can draw, and the degree to which those conclusions can be trusted.
🔍 Analogy — The Recipe Problem Think of operationalization like writing a recipe. If a recipe says "add some sugar," every baker will add a different amount, and the results will vary wildly. But if it says "add 150 grams of caster sugar," every baker is working from the same specification. In the same way, a researcher who says they are studying "stress" has left the concept vague. A researcher who says they are measuring stress as "self-reported score on the Perceived Stress Scale (PSS-10), administered after a 10-minute public speaking task" has given a precise, replicable specification. That precision is what makes science cumulative — others can follow the same recipe and check whether they get the same result.
Core Concepts
Before any data can be collected, a researcher must be precise about what they are studying. Psychology deals in concepts — constructs like "anxiety," "intelligence," "conformity," or "attachment" — that cannot be directly observed. To study them scientifically, these constructs must be translated into something measurable. This translation process is called operationalization, and it is one of the most important decisions a researcher makes.
📖 Key Definition — Operationalization Operationalization is the process of defining a psychological concept in terms of the specific procedures or measures used to observe or quantify it. An operationalized variable has a clear, precise definition that allows it to be measured consistently and replicated by other researchers.
Consider the concept of "aggression." In everyday language, aggression can mean anything from a raised voice to physical violence. For a researcher, this vagueness is a problem. If two researchers both claim to be studying aggression but are measuring it differently — one counting the number of times a child hits a Bobo doll, another