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Class 11 Presentation of Data: cheat sheet
CBSE Social Science. Presenting data in text, tables and diagrams: the parts of a table, bar and pie diagrams, histograms, frequency polygons, ogives and line graphs.
Key ideas
- Data can be presented in text (small data), tables (compact and exact) or diagrams (quick and attractive).
- A table has a number, title, captions (column headings), stubs (row headings), body, unit, source and note.
- Simple bar diagrams compare one set of figures; multiple bars put sets side by side; component bars split a total into parts.
- A pie diagram shows the shares of a whole as sectors of a circle.
- A histogram has touching rectangles on class intervals, and their areas stand for the frequencies; joining the mid-points of their tops gives a frequency polygon.
- Ogives are cumulative frequency curves: the less than ogive rises, the more than ogive falls, and they cross at the median.
- An arithmetic line graph shows a time series and its trend.
Remember
| Pie sector angle | part ÷ total × 360° (or per cent × 3.6) |
| Per cent from an angle | angle ÷ 360 × 100 |
| Histogram height (unequal classes) | frequency × standard width ÷ class width |
| Less than ogive | plot cumulative frequency against each UPPER limit |
| More than ogive | add from the bottom class upward; plot against each LOWER limit |
| Frequency polygon | plot (class mark, frequency) and join the points |
| Percentage change | (new − old) ÷ old × 100 |
Watch out
- Leaving gaps between histogram rectangles, or drawing a histogram for discrete data.
- Using the frequency as the height of a wider class without adjusting it.
- Forgetting to multiply the share by 360° for a pie diagram.
Worked example
Write the points of the more than ogive (lower limit, cumulative frequency) for: Class: 60–80, 80–100, 100–120, 120–140 Frequency: 17, 6, 17, 30
Working: add the frequencies from the bottom class upwards
Answer: (60, 70), (80, 53), (100, 47), (120, 30)
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