Data Types and Levels of Measurement
Classify qualitative and quantitative, primary and secondary data and identify nominal, ordinal and interval or ratio measurement.
How to study A-level Psychology
For every claim, identify the mechanism, supporting evidence, method, alternative explanation, practical implication and justified conclusion.
Core concepts
Concept 1
Qualitative data preserve meaning and context, whereas quantitative data support numerical comparison; either can be primary or secondary.
Exam cue: Classify the values actually recorded rather than the construct's everyday description.
Concept 2
Nominal data form categories, ordinal data preserve rank and interval or ratio data use equal numerical units.
Exam cue: Distinguish a rank from a score with equal intervals.
Concept 3
The operational measure and distribution determine which summary, graph and inferential procedure are appropriate.
Exam cue: Explain what information is lost when rich responses are coded into categories.
Targeted study blocks
Multi-board knowledge
Secure the shared psychological core
Learn the shared data classifications and levels of measurement because they govern representation, descriptive analysis and test choice on every board.
Scientific reasoning
Use evidence before reaching a judgement
Choose a data form that answers the aim, then acknowledge the precision, context and comparability gained or lost.
Risk pitfalls and guardrails
Equating qualitative with secondary data.
Guardrail: Do not memorise a study as an isolated story or assume that one board's named research and option choices apply nationally.
Calling every numerical code interval data.
Guardrail: Do not memorise a study as an isolated story or assume that one board's named research and option choices apply nationally.
Choosing a statistical procedure before identifying design and level of measurement.
Guardrail: Do not memorise a study as an isolated story or assume that one board's named research and option choices apply nationally.
Memory anchors
Qualitative data
Qualitative data record meanings, descriptions or categories rather than numerical magnitude.
Quantitative data
Quantitative data express observations numerically.
Primary data
Primary data are collected directly for the current research purpose.
Nominal level
Nominal measurement places observations into unordered categories.
Ordinal level
Ordinal measurement orders observations without assuming equal gaps.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
Which dataset is qualitative?
Why can qualitative data be valuable in psychology?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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