What is a Bar Graph?
A Bar Graph allows us to quickly understand and interpret information by using bars of uniform width.
Tip
Key Features:
- Uniform Width: All bars must be the same width.
- Equal Spacing: The gap between each bar must be the same.
- Height/Length: The height of the bar represents the frequency (number) of the data.
Reading a Bar Graph
Let’s analyze a bar graph showing traffic at a busy road crossing. Scale: 1 unit length = 100 vehicles.
Correction: The text mentions 1200 vehicles. Let’s render a horizontal bar graph as described in one of the book’s examples or a vertical one to fit.
Revised Visual (Vertical Bar Graph):
- Scale: 100px = 400 vehicles. Max 1200 = 300px.
Inference:
- Maximum Traffic: 7-8 AM (Longest bar).
- Minimum Traffic: 6-7 AM (Shortest bar).
- Total traffic between 8 and 10 AM: vehicles.
Drawing a Bar Graph
- Draw Axes: Draw a horizontal line (x-axis) and a vertical line (y-axis).
- Choose a Scale: Determine how many units 1 cm represents. (e.g., 1 unit = 100 vehicles).
- Mark Categories: Mark the items (e.g., time intervals) on the horizontal axis with equal gaps.
- Draw Bars: Draw vertical bars for each item. The height is determined by dividing the frequency by the scale.
- Example: If frequency is 600 and scale is 1 unit = 100, height = units.