Measures of Central Tendency
Mean
Mean = Sum of all values / Number of values Median
Middle value when data is ranked in order; for even n, average the two middle values Mode
Most frequently occurring value in a data set Cambridge International A Level Psychology 9990
🧠 Cambridge A Level Psychology Reference Sheet 2026
Essential reference for Cambridge A Level Psychology students — research methods statistics, core study summaries, evaluation frameworks, and essay structure.
Research Methods Key Studies Evaluation Frameworks Essay Structure
Our reference sheets are free to download — save this one as PDF for offline revision.
Aligned with the latest 2026 syllabus and board specifications. This sheet is prepared to match your exam board’s official specifications for the 2026 exam series.
Research Methods, Key Studies & Evaluation in One Reference Sheet
Cambridge A Level Psychology (9990) requires both scientific precision and analytical depth. This reference sheet consolidates the research methods formulas, core study summaries, evaluation frameworks, and essay structures you need to perform at the highest level across all components.
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Research methods statistics — formulas and when to use them
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Key study quick reference by topic area
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Evaluation frameworks for theories and studies
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Essay structure for extended response questions
Research Methods Formulas & Statistics
Know which statistical test to use and how to calculate each measure.
Measures of Dispersion
Range
Range = Highest value − Lowest value Standard Deviation
s = √(Σ(x − x̄)² / (n − 1)) (larger SD = more spread data) High SD indicates greater variability in scores; low SD indicates scores are clustered near the mean.
Correlation Coefficient
Spearman's rho (rs)
rs = 1 − (6Σd²) / (n(n²−1)) +1 = perfect positive correlation | 0 = no correlation | −1 = perfect negative correlation
Chi-Squared (χ²)
χ² = Σ [(O − E)² / E] O = Observed frequency, E = Expected frequency. Used for nominal data with independent groups.
Which Statistical Test to Use
Mann-Whitney U
Ordinal data | Independent groups | Looking for difference Wilcoxon T
Ordinal data | Repeated measures | Looking for difference Chi-squared
Nominal data | Independent groups | Looking for association/difference Spearman's rho
Ordinal/interval data | Looking for correlation Pearson's r
Interval data | Normal distribution | Looking for correlation Key Study Reference Guide
Know the aim, method, findings, and conclusions of each core study.
Approaches to Psychology
Behaviourism
Watson & Rayner (1920) — Little Albert. Classical conditioning of fear in an infant. Cognitive
Bartlett (1932) — War of the Ghosts. Memory is reconstructive, influenced by schemas. Biological
Raine et al. (1997) — PET scans of murderers. Brain differences in prefrontal cortex activity in violent offenders. Psychodynamic
Freud (1909) — Little Hans. Oedipus complex explaining phobia of horses. Social Psychology
Milgram (1963)
Obedience study — 65% of participants gave maximum 450V shock to a stranger when ordered by an authority figure. Zimbardo (1973)
Stanford Prison Experiment — situational factors influence behaviour; experiment stopped early due to distress. Memory
Atkinson & Shiffrin (1968)
Multi-store model: sensory register → STM → LTM. Limited STM (7±2 items, ~30s). Baddeley & Hitch (1974)
Working memory model: central executive, phonological loop, visuospatial sketchpad, episodic buffer. Developmental Psychology
Ainsworth (1970)
Strange Situation: secure (65%), insecure-avoidant (20%), insecure-ambivalent (15%) attachment types. Piaget
Four stages of cognitive development: sensorimotor (0–2), pre-operational (2–7), concrete operational (7–11), formal operational (12+). Evaluation Frameworks
Use these frameworks to evaluate theories, studies, and approaches systematically.
Evaluating Research Studies
Validity
Does it measure what it claims to measure? Internal validity (controlled) vs external validity (generalisability) Reliability
Can results be replicated? Inter-rater reliability for observational studies. Sample
Is the sample representative? Size, demographics, how recruited — affects generalisability. Ethics
Informed consent, right to withdraw, deception, debriefing, protection from harm — BPS guidelines. Evaluating Theories
Falsifiability
Can the theory be tested and potentially disproved? Empirical support
Is there research evidence to support the theory's claims? Explanatory power
How much behaviour does the theory explain? Determinism vs free will
Does the theory assume behaviour is determined by factors outside our control? Reductionism vs Holism
Reductionism
Explaining behaviour in terms of a single level (e.g., biological, conditioning) Holism
Considering multiple interacting levels of explanation Essay Structure for Psychology Questions
Extended response questions require structured argument with AO1 (knowledge) + AO2 (application) + AO3 (evaluation).
AO1 / AO2 / AO3 Balance
AO1
Describe the theory, study, or concept accurately and in detail AO2
Apply to a scenario, example, or real-world context AO3
Evaluate: strengths, limitations, supporting/contradicting evidence, ethical issues Extended Response Structure
Introduction
Define key terms and state your line of argument or focus Body paragraphs
Each covers one theory/study: describe (AO1) → apply (AO2) → evaluate (AO3) Conclusion
Weigh up competing evidence → state overall judgement with justification Evaluation Sentence Starters
A strength of this theory is... | A limitation is... | This is supported by research evidence from... | However, this can be criticised because... | This raises the issue of... How to Use This Reference Sheet
Boost your Cambridge exam confidence with these proven study strategies from our tutoring experts.
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Create Study Cards for Each Study
For every core study: aim → method → sample → findings → conclusions → evaluations. Practise retrieving all five from memory.
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Master Research Methods
Research methods questions appear on every paper. Know all statistical tests, their conditions for use, and how to interpret significance levels.
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Balance AO1 / AO2 / AO3
In extended essays, marks are split across description, application, and evaluation. Don't write only AO1 — examiners reward analysis and evaluation most.
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Link Studies to Approaches
Every study reflects an approach to psychology. Link studies to their assumptions (biological determinism, environmental learning, etc.) for higher-order marks.
Reference Sheet FAQ
Quick answers about this free PDF and how to use it for exam revision and active recall.
Is the Cambridge A Level Psychology Reference Sheet 2026 free to download as a PDF?
Yes. This Tutopiya formula sheet is free to use and you can download it as a PDF from this page for offline revision. There is no payment or account required for the PDF download.
What Psychology topics and equations does this formula sheet cover?
This page groups key Psychology formulas in one place for revision. Master Cambridge A Level Psychology (9990) with this 2026 reference sheet. Covers research methods statistics, key study reference guide, evaluation frameworks, and essay structure. Always cross-check with your official syllabus and past papers for your exam session.
Can I use this instead of the official exam formula booklet in the exam?
No. In the exam you must follow only what your exam board allows in the hall—usually the official formula booklet or data sheet where provided. This page is a revision and teaching aid, not a replacement for board-issued materials.
Who is this formula sheet for (Post-Secondary)?
It is written for students preparing for assessments at Post-Secondary in Psychology, including classroom revision, homework support, and independent study. Teachers and tutors can also share it as a quick reference.
How should I revise with this formula sheet?
Work through past paper questions, quote the correct formula before substituting values, and check units and notation every time. Pair this sheet with timed practice and mark schemes so you see how examiners expect working to be set out.
Where can I get more help with Psychology revision?
Explore Tutopiya’s study tools, past paper finder, and revision checklists linked from our tools hub, or book a trial lesson with a subject specialist for personalised support alongside this formula reference.
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This reference sheet aligns with Cambridge Assessment International Education International A Level Psychology (9990) syllabus content.
Always support evaluative points with specific research evidence and use correct psychological terminology throughout.