Knowledge Organiser: Graph Skills and Data Interpretation
Graph Types
- Line graph: continuous data over time
- Bar chart: discrete categories
- Histogram: frequency of grouped continuous data (bars touch)
- Pie chart: parts of a whole (proportions only)
- Scatter graph: correlation between two variables
- Climate graph: temperature (line) + precipitation (bars), 12 months
- Population pyramid: age-sex structure, males left / females right
- Choropleth: variable distributed across geographic areas
TACT Framework
- T — Trend: overall direction with start/end values
- A — Anomaly: data point that doesn't fit trend + reason
- C — Comparison: direct comparison of highest vs lowest with both values
- T — Total/Terminology: specific figures with units; precise vocabulary
- Correlation ≠ causation — ALWAYS
- 3–5 well-chosen figures beat 12 passively listed ones
Climate Graph Steps
- 1. Hottest month (°C) and coldest month (°C)
- 2. Annual range = hottest − coldest
- 3. Wettest month (mm) and driest month (mm)
- 4. Total annual precipitation (mm)
- 5. Classify climate type from the pattern
- Small range (<10°C) = maritime/tropical; large range (>20°C) = continental/desert
Population Pyramid and Stats
- Wide base = high birth rate (LIC); narrow base = low birth rate (HIC)
- Tapers fast upward = high death rate / low life expectancy
- Stays wide = low death rate / high life expectancy (HIC)
- Bulge in working age = immigration or baby boom
- Mean: best for evenly distributed data
- Median: best when outliers present (income, house prices)
- IQR = Q3 − Q1 (spread of middle 50%)
- % change = ((new−old) ÷ old) × 100
Common Mistakes
- Describing numbers instead of patterns: Don't list every figure — identify the overall trend, then support with specific values (highest, lowest, anomaly)
- Confusing bar charts and histograms: Histograms have touching bars and show continuous data grouped into classes; bar charts have gaps and show discrete categories
- Stating "correlation = causation": A scatter graph shows a relationship between variables — always use the word "suggests" and acknowledge other factors may be involved
- Missing units or axes on drawn graphs: Every drawn graph needs a title, labelled axes with units, a scale starting at zero (unless specified), and a key if multiple data sets are shown
- Using mean when outliers are present: For skewed data such as income or house prices, use the median — the mean is distorted by extreme values
Memory Aid
- Hottest month — identify the peak of the temperature line, note month and °C value
- Coldest month — identify the trough of the temperature line, note month and °C value, calculate annual range = H − C
- Wettest month — identify the tallest bar, note month and mm value
- Calculate total annual precipitation — add bars or estimate, note mm value and seasonal pattern
- WIDE base = HIGH birth rate
- NARROW base = LOW birth rate
- TAPERS fast upward = HIGH death rate / LOW life expectancy (LIC)
- STAYS wide upward = LOW death rate / HIGH life expectancy (HIC)
- BULGE in working age = immigration or baby boom cohort
- PINCH in working age = emigration or one-child policy effect
- Mean — for normal, evenly spread data with no extreme values
- Income / inequality data — use Median, not Mean (outliers distort)
- List all values if asked for mode — it is the most frequently repeated number
- Outliers present? → Choose Median or IQR over Mean or Range