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NCERT Class XI Mathematics - Statistics - Solutions

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Question : 6
Total: 34
xi 10 30 50 70 90
fi 4 24 28 16 8

Solution:  
xi 10 30 50 70 90
fi 4 24 28 16 8 80
fixi 40 720 1400 1120 720 4000
|xi−50| 40 20 0 20 40
fi|xi−50| 160 480 0 320 320 1280

Mean (
−
x
) =
1
N
n
Σ
i=1
fixi =
1
80
×4000 = 50
∴ Mean deviation about mean =
1
N
n
Σ
i=1
fi|xi−
−
x
| =
1
80
 × 1280 = 16
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