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प्रश्न
Find the mean of the following frequency distribution:
| Class: | 10 – 15 | 15 – 20 | 20 – 25 | 25 – 30 | 30 – 35 |
| Frequency: | 4 | 10 | 5 | 6 | 5 |
उत्तर
| Class | Mid-point `(bbx_i)` |
`bb(f_i)` | `bb(d_i = x_i - A)` | `bb(f_i d_i)` |
| 10 – 15 | 12.5 | 4 | – 10 | – 40 |
| 15 – 20 | 17.5 | 10 | – 5 | – 50 |
| 20 – 25 | 22.5 = A | 5 | 0 | 0 |
| 25 – 30 | 27.5 | 6 | 5 | 30 |
| 30 – 35 | 32.5 | 5 | 10 | 50 |
| Total | `sumf_i` = 30 | `sumf_i d_i` = – 10 |
Here, assumed mean, A = 22.5
Mean = `A + (sumf_i d_i)/(sumf_i)`
= `22.5 + (-10)/30`
= 22.5 – 0.33
= 22.17
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