
Chapter 4
140
4.4.15.2 Standard Deviation and Variance for Discrete and Continuous Frequency
Distributions
In the case of a discrete series, the formula discussed above will vary slightly. In this case, we
have to compute an additional term:
fx x
ii
i
n
−
=
∑
2
1
. The formula for sample standard deviation
and sample variance for a discrete frequency distribution is given as
Sample standard deviatio
here()
()
s
fx x
N
ii
i
n
i
i
n
=
−
−
=
=
=
∑
∑
2
1
1
1
Sample variance where()
()
s
fx x
N
ii
i
n
i
i
n
2
2
1
1
1
=
−
−
=
=
=
∑
∑
Standard deviation and variance for a continuous frequency distribution can also be computed
by applying the same procedure we have adopted for a discrete frequency distribution. ...