Page 236 - DSOC404_METHODOLOGY_OF_SOCIAL_RESEARCH_ENGLISH

Methodology of Social Research

notes 22 +2 4
24 +4 16

26 +6 36
28 +8 64
30 +10 100

32 +12 144
N = 12 Sd’ = 12 S d = 2 584

S 2  S ' d '  d 2
σ = −   N   N
According to question—
Sd´ = 584
2
Sd´ = 12
N = 12

584  12 2
−
σ = 12 −   12  = 48.66 (1) 2
= 48.66 1 = 47.66
−
σ = 6.9 (Approx.)

(b) Discrete series

Example 5 the data shows score and their frequency as depicted below. find the
standard deviation.
score 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5

frequency 1 0 0 2 1 2 3 2 3 4 6 8 7 5 2 1 3

solution—
Direct Method
S fd 2
Formulae σ =
N
score frequency f x x = fx Variation d(x – M) F x d = fd fd 2
(X) (f) M = 11 fd x d
21 1 21 10 10 100

20 0 0 9 0 0
19 0 0 8 0 0
18 2 36 7 14 98

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