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5. It should have sampling stability
6. It should not be unduly affected by extreme values.
Sikkim Manipal University Page No. 186 Research Methodology Unit 11 Measures of Dispersion
1. Range
2. Quartile deviation
3. Mean deviation
4. Standard deviation
5. Lorenz curve
Range, Quartile deviation, Mean deviation and Standard deviation are
mathematical measures of dispersion. Lorenz curve is a graphical measure
of dispersion.
Measures of dispersion can be absolute or relative. An absolute measure of
dispersion is expressed in the same unit of the original data. When two sets
of data are expressed in different units, relative measures of dispersion are
used for comparison. A relative measure of dispersion is the ratio of
absolute measure to an appropriate average.
The following are the important relative measures of dispersion.
1. Coefficient of range
2. Coefficient of Quartile deviation
3. Coefficient of Mean deviation
4. Coefficient of Standard deviation
Range
Range is the difference between the lowest and the highest value.
Symbolically, range = highest value – lowest value Range = H–L H = highest value L = lowest value Relative measure of dispersion is coefficient of range. It is obtained by the
following formula.
Coefficient of range = Sikkim Manipal University (H – L) / (H + L) Page No. 187 Research Methodology Unit 11 1. Calculate of range of the following distribution, giving income of 10
workers. Also calculate the coefficient of range.
25 37 40 23 58 75 89 20 81 Range = H–L H = highest value = 95 L = lowest value = 20 Range = 95 –20 = 75 Coefficient of range = (H – L) / (H + L) = (95 –20) / (95 +20) = 75/ 115 = 95 .6521 Range is simple to understand and easy to calculate. But it is not based on
all items of the distribution. It is subject to fluctuations from sample to
sample. Range cannot be calculated for openended series.
Quartile Deviation
Quartile deviation is defined as inter quartile range. It is based on the first
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 Spring '10
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