Explain the presentation of data by bar graphs and pie charts with suitable examples.

1. 1 · Open in two lines. Diagrams present data visually so that comparisons are seen at a glance. Bar graphs and pie charts are the most common.
2. 2 · Bar graph and its rules.
   • Bars of equal width and gap.
   • Axis starts at zero.
   • Suitable scale.
   • Title, labels and key.
3. 3 · Types of bar graph with sketches.
   • Simple.
   • Multiple.
   • Sub-divided.
   • Percentage.
   • Deviation.
   • Broken.
4. 4 · Pie chart and its formula. A circle divided into sectors; angle = value ÷ total × 360°; start at 12 o'clock and go clockwise.
5. 5 · Work an example. Anaemia grades of 120 girls: 135°, 117°, 99°, 9° (total 360°). Draw and label the pie.
6. 6 · Compare the two. Bar graph for comparing sizes and many categories; pie chart for parts of one whole with few parts.
7. 7 · Nutrition example. Pie chart for the share of energy from food groups; multiple bars for anaemia before and after a mid-day meal programme.
8. 8 · Close in one line. Choose the diagram that makes the main message of the data easiest to see.

Scoring tip: Show the pie-chart working line by line and check that the angles add up to 360°. Neat sketches beat long text.