Find the mean, variance and standard deviation using short-cutmethod
| Height in cms | No. of children |
| 70-75 | 3 |
| 75-80 | 4 |
| 80-85 | 7 |
| 85-90 | 7 |
| 90-95 | 15 |
| 95-100 | 9 |
| 100-105 | 6 |
| 105-110 | 6 |
| 110-115 | 3 |
| Class Interval | Frequency fi | Mid-point xi |
| yi2 | fiyi | fiyi2 |
| 70-75 | 3 | 72.5 | –4 | 16 | –12 | 48 |
| 75-80 | 4 | 77.5 | –3 | 9 | –12 | 36 |
| 80-85 | 7 | 82.5 | –2 | 4 | –14 | 28 |
| 85-90 | 7 | 87.5 | –1 | 1 | –7 | 7 |
| 90-95 | 15 | 92.5 | 0 | 0 | 0 | 0 |
| 95-100 | 9 | 97.5 | 1 | 1 | 9 | 9 |
| 100-105 | 6 | 102.5 | 2 | 4 | 12 | 24 |
| 105-110 | 6 | 107.5 | 3 | 9 | 18 | 54 |
| 110-115 | 3 | 112.5 | 4 | 16 | 12 | 48 |
| 60 | 6 | 254 |
Mean, 
