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NCERT Class XI Mathematics - Statistics - Solutions

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Question : 17
Total: 34
xi 92 93 97 98 102 104 109
fi 3 2 3 2 6 3 3

Solution:  
xi fi fixi (xi−100) (xi−100)2 fi(xi−100)2
92 3 276 - 8 64 192
93 2 186 - 7 49 98
97 3 291 - 3 9 27
98 2 196 -2 4 8
102 6 612 2 4 24
104 3 312 4 16 48
109 3 327 9 81 243
22 2200 640

Mean (
−
x
) =
1
N
n
Σ
i=1
fixi =
1
22
 × 2200 = 100
Variance (σ2) =
1
N
n
Σ
i=1
fi(xi−
−
x
)2 =
1
22
 × 640 = 29.09
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