Statistical methods

Measures of central tendency

• Mean: total ÷ number of items.
• Median: middle value when arranged in order.
• Mode: most frequent value.
• Range: highest - lowest.

Presenting data

• Simple bar graph: one set of data.
• Comparative bar graph: two or more sets side by side.
• Divided (compound) bar graph: one bar split into parts.
• Line graph: change over time (e.g. temperature).
• Pie chart (divided circle): parts of a whole.

Angle = (value ÷ total) × 360°

Example: Tea 40, coffee 20, maize 60 (total 120). Tea angle = 40/120 × 360 = 120°.

Advantages and disadvantages

• Pie charts show proportions clearly but are hard to read when there are many small parts.
• Line graphs show trends, but only for continuous data.

Tips

Always give a title, key, scale and labelled axes.