Descriptive Statistics, Displays and Distributions
Summarise and display psychological data with appropriate measures of central tendency, dispersion, graphs and distribution shapes.
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
Mean, median and mode summarise different aspects of a dataset and differ in sensitivity to skew and extreme values.
Exam cue: Show working, units and sensible precision for every calculation.
Concept 2
Range and standard deviation represent dispersion with different levels of information and sensitivity.
Exam cue: Select the display from the measurement level and purpose, not visual preference.
Concept 3
Tables, bar charts, histograms, line graphs and scatter diagrams serve different variables and claims; normal and skewed distributions link centre and shape.
Exam cue: Compare groups using both centre and spread rather than a mean alone.
Targeted study blocks
Multi-board knowledge
Secure the shared psychological core
Practise Level 2 arithmetic, central tendency, dispersion, frequency displays, graphs and distribution shapes within psychological contexts.
Scientific reasoning
Use evidence before reaching a judgement
Use a descriptive statistic to reveal the pattern but do not mistake description for evidence that an effect is statistically significant or causal.
Risk pitfalls and guardrails
Using a histogram for unordered categories.
Guardrail: Do not memorise a study as an isolated story or assume that one board's named research and option choices apply nationally.
Assuming a higher mean proves every participant scored higher.
Guardrail: Do not memorise a study as an isolated story or assume that one board's named research and option choices apply nationally.
Describing standard deviation only as a range.
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
Mean
The mean is the arithmetic total divided by the number of scores.
Median
The median is the middle score after values are ordered.
Standard deviation
Standard deviation summarises typical spread around the mean.
Histogram
A histogram represents continuous interval data with adjoining bars.
Positive skew
In a positive skew the long tail extends toward higher values.
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
Five recall scores are 4, 6, 8, 10 and 12. What is the mean?
The ordered scores are 2, 4, 4, 9 and 15. What is the median?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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