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0 votes
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in Statistics by (15.9k points)

Find the mean deviation about the median for the following data: 

1. 

xi 5 7 9 10 12 15
fi 8 6 2 2 2 6

2. 

xi 15 21 27 30 35
fi 3 5 6 7 8

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1 Answer

0 votes
by (15.3k points)

1.

xi fi c.f |xi - 7| |xi - 7| fi
5 8 8 2 16
7 6 14 2 4
10 2 18 3 6
12 2 20 5 10
15 6 26 8 48
26 84

 \(\frac{\sum^{n}_{i=1}}{2}\) = \(\frac{26}{2}\) = 13

The c.f just greater than 13 is 14 and corresponding value of x is 7. 

Therefore; median, M = 7

Hence; M.D about median

\(\frac{\displaystyle\sum_{i=1}^{n} f_i |x_i - M|}{\displaystyle\sum_{i = 1}^{n} f_i}\)

\(\frac{84}{26} = 3.23\)

2.

xi fi c.f |xi - 30| |xi - 30| fi
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
29 148

 \(\frac{\sum^{n}_{i=1}}{2}\) = \(\frac{29}{2} = 14.5\)

The c.f just greater than 14.5 is 21 and corresponding value of x is 30. Therefore; median, M = 30

Hence; M.D about median

\(\frac{\displaystyle\sum_{i=1}^{n} f_i |x_i - M|}{\displaystyle\sum_{i = 1}^{n} f_i}\)

\(\frac{148}{29} = 5.1\)

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