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,