2. The difference between the largest and smallest value of data set is
called range. It is the simplest measure of spread.
Range (R) = Largest value (L) – Smallest Value (S)
Weight of students: 55, 89, 65, 74, 79, 98, 89, 68
Range = 98 - 55 = 43
Range
Largest ValueSmallest Value
While range is having limited use as a measure of spread. It act as check of the upper and
lower limits of data, and if any variable had crossed that limit.
Example: if the range of a data of age of school student's is 24, that shall indicate a mistake.
3. Range of grouped data
(Discrete Series)
Ignore Frequency and calculate range for variable like individual
series.
Age 5 6 7 8 9 10
No of students 10 20 22 15 7 6
Age 5 6 7 8 9 10
Largest value = 10, Lowest value = 5
Range = L - S = 10 - 5 = 5
4. Range of grouped data
(Continuous Series)
Ignore Frequency and calculate range for variable like individual
series.
Largest value = Upper limit of highest class (in this case 30-35).
Smallest value = Lower limit of lowest class (in this case 5- 10).
Range = L - S = 35 - 5 = 30
Age 5-10 10-15 15-20 20-25 25-30 30-35
No of participants 10 20 22 15 7 6
Age 5-10 10-15 15-20 20-25 25-30 30-35
5. Limitation of range
We cant draw any inference of population range form the
range of the sample.
Range is based on two extreme observations. It gives no weight
to the central values of the data. Hence it’s a poor measure of
dispersion
Group A: 25, 26, 27, 29, 75
Group B: 25, 55, 45, 60, 75
Range for both groups is 50 (75-25) still its clearly visible that B is
having higher dispersion.
6. Limitation of range
Due to this limitation’s range doesn’t enjoy any prominent place in statistical
analysis, still it’s useful is quality control.
Range is used to maintain the quality of products produced in factories. The
quality of products need’s kept within a certain range of values. Which is
considered to accepted range.
.
7. Coefficient of Range
This is a relative measure of dispersion and is based on the value of
the range.
Coefficient of Range =
L = Largest values
S= Smallest Value
L- S
L+S
8. Coefficient of Range
Example:
Weight of students: 55, 89, 65, 74, 79, 98, 89, 68
Smallest Value Largest Value
Coefficient of Range =
98 - 55
98 +55
Coefficient of Range =
L- S
L+S
43
153
= = 0.28
Why Coefficient?
9. . Coefficient of Range
Term A (Max 40) 15 25 30 26 20 22
Term B( Max 100) 65 75 85 82 88 72
Range (Term A) = 30-15 = 15
Range (Term B) = 88-65 = 23
We can conclude that marks for term B are more diverse, since range is higher.
Because the base is not same.
10. .
Term A (Max 40) 15 25 30 26 20 22
Term B( Max 100) 65 75 85 82 88 72
Coefficient of range =
L- S
L+S
=Coefficient of range (Term A) 30-15
30+15
15
45
= = 0.33
Now we get the right picture that Term A is more diverse.
Coefficient of Range
Coefficient of range (Term B)
88-65
88+65
23
153
= = 0.15=
