The necessary table to calculate S.D. is as below:
d,
C.I.
Class marks, xi
с
fi
fid,
Id?
where a = 12.5, c = 5
0 – 5
2.5
6
-2
-12
24
5-10
7.5
10
-1
-10
10
10 – 15
12.5
12
0
0
0
15 – 20
17.5
10
1
10
10
20-25
22.5
8
2
16
32
Σf, = 46
Ef;d, = 4
Σ 1,d = 76
Answer:
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