Charts & Diagrams
Year 8 📈 Statistics & Probability Bar charts, pie charts, stem-and-leaf, frequency diagrams.
📊 Bar Charts and Pie Charts
Bar charts display frequency using the height of bars. Pie charts show proportions using angles — the whole circle represents 100%.
⚡ Pie Chart Angle
$$\text{Angle} = \frac{\text{frequency}}{\text{total}} \times 360°$$Example: 12 out of 30 students prefer Science: angle $= \frac{12}{30} \times 360 = 144°$
📈 Line Graphs and Time Series
Line graphs show how a quantity changes over time. Points are plotted and joined in order.
When interpreting a time series, look for: trends (rising/falling overall), seasonal patterns (regular repeating cycles), and anomalies (unexpected values).
Example: A shop's monthly sales graph peaks each December (Christmas) and dips in January — this is a seasonal pattern.
📉 Stem-and-Leaf Diagrams
A stem-and-leaf diagram displays raw data in order, making it easy to find the median and range.
Example: Data: 23, 27, 31, 35, 38, 42
2 | 3 7\n3 | 1 5 8\n4 | 2Key: 2|3 = 23. Median $= \frac{31+35}{2} = 33$, Range $= 42-23 = 19$
Back-to-back stem-and-leaf diagrams place two data sets on either side of a shared stem for easy comparison.
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Interactive Demonstration — Charts & Diagrams
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