Calculate the mean deviation about the median of the following frequency distribution:
xi | 5 | 7 | 9 | 11 | 13 | 15 | 17 |
fi | 2 | 4 | 6 | 8 | 10 | 12 | 8 |
We will first calculate the median for the data.
xi | fi | Cumulative Frequency (CF) | di=xi−A =xi−13 | fidi |
5 | 2 | 2 | 8 | 16 |
7 | 4 | 6 | 6 | 24 |
9 | 6 | 12 | 4 | 24 |
11 | 8 | 20 | 2 | 16 |
13 | 10 | 30 | 0 | 0 |
15 | 12 | 42 | 2 | 24 |
17 | 8 | 50 | 4 | 32 |
N=∑fi=50 | ∑fidi=136 |
Here,
N2=502=25
The cumulative frequency just greater than 25 is 30 and the corresponding value of x is 13.
∴ Median, M=13
Mean deviation about median, MD=∑fidiN
=13650=2.72