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Question
Construct a frequency polygon for the following data:
| Class-Intervals | 10-14 | 15-19 | 20-24 | 25-29 | 30-34 |
| Frequency | 5 | 8 | 12 | 9 | 4 |
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Solution
The class intervals are inclusive. We will first convert them into the exclusive form.
| Class-Interval | Frequency |
| 9.5-14.5 | 5 |
| 14.5-19.5 | 8 |
| 19.5-24.5 | 12 |
| 24.5-29.5 | 9 |
| 29.5-34.5 | 4 |
Steps:
- Draw a histogram for the given data.
- Mark the mid-point at the top of each rectangle of the histogram drawn.
- Also, mark the mid-point of the immediately lower class-interval and the mid-point of the immediately higher class-interval.
- Join the consecutive mid-points marked by straight lines to obtain the required frequency polygon.
The required frequency polygon is as follows:
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