Question -
| Marks | 10-20 | 20-30 | 30-40 | 40-50 | 50-60 | 60-70 | 70-80 | 80-90 |
| No. of students | 8 | 10 | 15 | 25 | 20 | 18 | 9 | 5 |
Answer -
To find the mean deviation from the mean, firstly let uscalculate the mean.
By using the formula,
= 5390/110
= 49
| Class Interval | xi | fi | Cumulative Frequency | |di| = |xi – M| | fi |di| |
| 10-20 | 15 | 8 | 120 | 34 | 272 |
| 20-30 | 25 | 10 | 250 | 24 | 240 |
| 30-40 | 35 | 15 | 525 | 14 | 210 |
| 40-50 | 45 | 25 | 1125 | 4 | 100 |
| 50-60 | 55 | 20 | 1100 | 6 | 120 |
| 60-70 | 65 | 18 | 1170 | 16 | 288 |
| 70-80 | 75 | 9 | 675 | 26 | 234 |
| 80-90 | 85 | 5 | 425 | 36 | 180 |
| | N = 110 | Total = 5390 | | Total = 1644 |
N = 110
MD=
= 1/110 × 1644
= 14.94
∴ Themean deviation is 14.94