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प्रश्न
Calculate the mean of the following frequency distribution :
| Class: | 10-30 | 30-50 | 50-70 | 70-90 | 90-110 | 110-130 |
| Frequency: | 5 | 8 | 12 | 20 | 3 | 2 |
उत्तर
| Class | frequency (fi) | Class mark(xi) | fixi |
| 10-30 | 5 | `(10+30)/2 = 20` | 100 |
| 30-50 | 8 | `(30+50)/2 = 40` | 320 |
| 50-70 | 12 | `(50+70)/2 = 60` | 720 |
| 70-90 | 20 | `(70+90)/2 = 80` | 1600 |
| 90-110 | 3 | `(90+110)/2 = 100` | 300 |
| 110-130 | 2 | `(110+130)/2 = 120` | 240 |
| `sumf_i = 50` | `sumf_ix_i = 3280` |
Using: Mean = `(sumf_ix_i)/(sumf_i)`
substituting the values in the formula
mean = `3280/50 = 65.6`
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