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Quartile Deviation

Quartile deviation is another measure of dispersion. It is given by Description: 96678.png 



Relative measure of dispersion based on quartiles is the coefficient of quartile deviation (Q.D.).


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The quartiles of a variable are 45, 52 and 65, respectively. Find its quartile deviation and coefficient of quartile deviation.
Given: Q1 = 45, Q2 = 52, Q3 = 65
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  1. It is easy to calculate.
  2. It can be easily understood.
  3. It is not affected by the extreme values.
  4. It has a special utility in measuring variation in case of frequency distribution with open-end classes at both ends.


  1. It is not based on all the observations.
  2. It is not the representative value of data.
  3. It is not capable of algebraic treatments.
  4. It is affected by sampling fluctuations.
    It cannot be regarded as measure of dispersion as it really does not show the scatteredness around an average but rather a distance on a scale.

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