1.1.4—Measurement
- Syllabus
- First assessment 2027
- Objective
- 1.1.4
- Level
- SL
Measurement turns a construct into observable evidence
Psychological constructs such as stress or memory cannot always be observed directly. Operationalization states exactly how a construct will be manipulated or measured, producing quantitative data such as scores or qualitative data such as interview accounts.
Reliability asks whether a procedure gives consistent results; validity asks whether it measures the intended construct and supports the claim. Direct behavioural or physiological measures and indirect self-reports each have strengths and limitations. Triangulation compares methods, data sources or investigators to test whether conclusions converge.
A study might operationalize stress using a standardized questionnaire score and a clearly defined behaviour during a task. Consistent scoring supports reliability; evidence that the indicators represent stress rather than general discomfort supports validity; an interview can add qualitative meaning and reveal disagreement between measures.
A precise number is not automatically an objective or valid measure. State the construct, operational definition, data type and source, then evaluate reliability, validity, reactivity, bias and whether triangulation genuinely examines the same phenomenon.