Eg. : Find out the range of the data : 27, 28, 34, 36, 39, 59
Range = Maximum value – Minimum value
= 59 – 27 = 32
- Standard deviation
Standard deviation is the square root of the mean of the squares of the differences of
individual scores from the mean. Standard deviation is denoted by the Greek letter
σ (Sigma). It can be obtained by the formula
2 2
N
⎜ ⎞
⎝
σ = Σ ⎛Σ
It is also obtained using the formula, nd
∑^2
σ=
where d = x –^ x and x is the mean.
The idea of standard deviation may be explained orally laying emphasis on the
memorization of the formula and knowing of its components. A thorough explanation
of the idea with the aid of a model problem will be useful to explain this concept.
14 196
22 484
981
15 225
20 400
17 289
12 144
11 121
x = 120 ∑ x^2 = 1940
xx^2
