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Question
In a study of dental problem, the following data were obtained.
| Ages | 0 − 10 | 10 − 20 | 20 − 30 | 30 − 40 | 40 − 50 | 50 − 60 | 60 − 70 | 70 − 80 |
| No. of patients | 5 | 13 | 25 | 14 | 30 | 35 | 43 | 50 |
Represent the above data by a frequency polygon.
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Solution
Finding the midpoints of the class interval we get.
| Ages | Mid point (x) | No. of patients |
| 0 – 10 | 5 | 5 |
| 10 – 20 | 15 | 13 |
| 20 – 30 | 25 | 25 |
| 30 – 40 | 35 | 14 |
| 40 – 50 | 45 | 30 |
| 50 – 60 | 55 | 35 |
| 60 – 70 | 65 | 43 |
| 70 – 80 | 75 | 50 |
The points to be plotted are A(5, 5), B(15, 13), C(25, 25), D(35, 14), E(45, 30), G(65, 43), H(75, 50) to obtain the frequency polygon ZABCDEFGHI.
Where I imagined class between 80 and 90.
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