Chapter 4 — Data Handling

Chapter 4 of the Class 8 Maths NCERT textbook, "Data Handling", teaches how to organize, represent, and interpret data using pictographs, bar graphs, double bar graphs, and pie charts (circle graphs). It also introduces probability, covering random experiments, equally likely outcomes, and how to calculate the probability of events.

• Choosing a representation — Pictographs, bar graphs and double bar graphs each suit different tasks — from symbol-based counts to comparing two datasets — teaching students to match the visualisation to the story the data tells.
• Wholes as pie charts — Pie charts split a circle into sectors proportional to parts of a whole, with each sector's central angle computed as its share of 360° — connecting proportion directly to a picture.
• Chance and probability — Random experiments introduce equally likely outcomes, and probability is quantified as favourable outcomes over total outcomes, with repeated trials (like coin tosses tending to 50:50) building intuition for chance.

1. 01A pictograph uses symbols to represent data, where one symbol stands for a fixed quantity (e.g., one symbol = 100 cars)
2. 02A bar graph displays data using bars of uniform width with heights proportional to values; used for comparing different categories
3. 03A double bar graph shows two sets of data simultaneously for easy comparison between related categories
4. 04A pie chart (circle graph) divides a circle into sectors, where sector size is proportional to the data it represents
5. 05To draw a pie chart, calculate the central angle for each sector using: Central angle = (Value/Total) × 360°
6. 06A random experiment is one whose outcome cannot be predicted in advance; examples include tossing a coin, rolling a die, or drawing a ball from a bag
7. 07Outcomes are equally likely when each outcome has the same chance of occurring, verified by repeating experiments many times (e.g., coin tosses approach 50:50)
8. 08Probability formula: Probability of event = (Number of favorable outcomes) / (Total number of equally likely outcomes)