Chapter 4: Data Handling and Presentation
Every day we meet numbers about the world: cricket scores, rainfall, prices, votes. In this chapter we collect our own data, sort it with tally marks, and show it as pictographs and bar graphs, so that anyone can understand it at a glance, and nobody is fooled by a tricky graph.
In this chapter you will
- collect data and organise it with tally marks
- read and draw pictographs with a key
- read bar graphs and draw them with a good scale
- make graphs that are clear and honest
Topics
- Collecting and Organising Data NCERT 4.1
Data: facts, numbers or observations that give information.
- Pictographs NCERT 4.2
A pictograph shows data with pictures; the key tells what one symbol stands for.
- Bar Graphs NCERT 4.3
Bar graph: bars of equal width and equal gaps; the height shows the number.
- Drawing a Bar Graph NCERT 4.4
Bar height = number ÷ scale. The scale must start at 0.
- Artistic and Aesthetic Considerations NCERT 4.5
Heights: vertical bars (columns). Lengths along the ground: horizontal bars.
Key words
- Data
- facts, numbers or observations that give information
- Tally mark
- a line for each answer; every 5th crosses the four before it
- Frequency
- how many times a value or answer occurs
- Pictograph
- data shown with pictures or symbols
- Key (scale)
- what one symbol or one unit length stands for
- Bar graph
- bars of equal width whose heights show numbers
Summary
- Data is information we collect: answers, counts and measurements.
- Tally marks help us count data in fives; the count for each group is its frequency.
- In a pictograph each symbol stands for a fixed number, given by the key; half a symbol shows half of it.
- In a bar graph, bars of equal width stand on a scale that starts at 0; taller bars mean bigger numbers.
- A good scale, clear colours and the right direction (columns for heights) make a graph easy to read; a graph that does not start at 0 can trick the eye.