Reading and Interpreting Histograms – Examples with Solutions
This tutorial presents worked examples with clear explanations on how to read and interpret histograms commonly used in statistics.
Example 1
The histogram below shows the distribution of heights (in cm) for 30 people.
- How many people have heights between 159.5 and 169.5 cm?
- How many people have heights less than 159.5 cm?
- How many people have heights more than 169.5 cm?
- What percentage of people have heights between 149.5 and 179.5 cm?
Solution to Example 1
- 7 people
- 9 + 6 = 15 people
- 5 + 2 + 1 = 8 people
- (9 + 7 + 5) ÷ 30 = 0.7 = 70%
Example 2
The histogram below shows the cholesterol levels (in mg/dL) of 200 people.
- How many people have cholesterol between 205 and 210 mg/dL?
- How many people have cholesterol less than 205 mg/dL?
- What percentage have cholesterol greater than 215 mg/dL?
- How many people have cholesterol between 205 and 220 mg/dL?
Solution to Example 2
Note: The vertical axis shows relative frequency.
- 0.2 × 200 = 40 people
- (0.05 + 0.1) × 200 = 30 people
- 0.25 + 0.05 = 0.3 = 30%
- (0.2 + 0.35 + 0.25) × 200 = 160 people
Example 3
The histogram below shows the fuel efficiency (in miles per gallon) of 110 cars.
- How many cars have efficiency between 15 and 20 mpg?
- How many cars have efficiency greater than 20 mpg?
- What percentage of cars have efficiency less than 20 mpg?
Solution to Example 3
- 35 cars
- 25 + 15 = 40 cars
- (15 + 20 + 35) ÷ 110 = 0.636 = 63.6%
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