xi | fi | Cumulative frequency | |xi−M| | fi|xi−M| |
15 | 3 | 3 | 15 | 45 |
21 | 5 | 8 | 9 | 45 |
27 | 6 | 14 | 3 | 18 |
30 | 7 | 21 | 0 | 0 |
35 | 8 | 29 | 5 | 40 |
Total | 29 | | | 148 |
Here N=29 (odd)Median =(N+12)thobservation
i.e. M=(29+12)thobservation
⇒M=15thobservation
Since, 15 occurs in the cumulative frequency 21. The corresponding observation is 30.
Hence, M=30
Mean deviation about median =∑fi|xi−M|∑fi