Class 9 Maths – Statistics

12.1 Graphical Representation of Data

• Statistics: The study of collection, organization, analysis, and interpretation of data.
• Graphical representation helps visualize data easily.

Common Graphical Methods

1. Bar Graphs
   • Represent discrete data using rectangular bars.
   • Height of each bar = frequency of the category.
2. Histogram
   • Similar to bar graph but for continuous data.
   • Bars touch each other.
3. Frequency Polygon
   • Points representing frequencies are joined by straight lines.
   • Helps compare data sets quickly.
4. Pie Chart
   • Data is represented in a circle divided into sectors.
   • Angle of sector =
   $$\text{Sector angle} = \frac{\text{Frequency}}{\text{Total frequency}} \times 360^\circ$$Sector angle=Total frequencyFrequency​×360∘

Steps to Draw a Graph

1. Collect data and make a frequency table.
2. Choose type of graph depending on data.
3. Label axes and scale properly.
4. Plot points, draw bars, or sectors.
5. Title the graph.

Advantages of Graphical Representation:

• Easy to interpret data
• Helps in comparison
• Makes trends visible

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