Statistical diagrams

Edexcel Foundation papers always include a chart-reading or chart-construction question. Higher papers may use these as warm-up questions or as the basis for a multi-part inference question.

Bar charts

For categorical or discrete data. Bars separated (gaps between bars). Equal width bars. Y-axis is frequency.

Edexcel marking on construction:

• Linear scale labelled ⇒ B1 (or C1) for axes.
• Bars correctly drawn at correct heights ⇒ M1 / A1.
• Title or labelled axes ⇒ communication mark.

Pie charts

A circle divided into sectors; sector angle = (frequency / total) × 360°.

Worked example: 30 students chose subjects: Maths 9, Science 12, Arts 6, Sport 3.

• Maths: 9/30 × 360 = 108°.
• Science: 12/30 × 360 = 144°.
• Arts: 6/30 × 360 = 72°.
• Sport: 3/30 × 360 = 36°.
• Total: 108 + 144 + 72 + 36 = 360° ✓.

Reading a pie chart: angle ÷ 360 × total = frequency for that sector.

Pictograms

A pictogram uses symbols (each representing a fixed frequency, e.g. one star = 4 people). Always include a key.

To read: count symbols × the key value. Edexcel often asks to draw additional symbols where a half- or quarter-symbol is required.

Frequency tables (linked to S2)

See P1 for two-way tables and frequency-table mean calculations.

Comparing two distributions

Use any of:

• Compare averages (mean, median, mode).
• Compare spread (range, IQR).
• Provide one comment about each (e.g. "the mean of A is higher, so the average score is higher" + "the range of A is larger, so scores are more spread out").

Edexcel exam tip

Pie chart angles must sum to 360°. Always check before claiming a sector value. If your angles sum to 359° or 361°, you've rounded a fraction wrongly somewhere — go back.