Class 11 Maths Statistics Quartile deviation

Quartile deviation

It is based on the lower quartile and the upper quartile. The difference is called the inter quartile range. The difference divided by is called semi-inter-quartile range or the quartile deviation.

 Quartile Deviation (Q.D)  = (Q3 – Q1 )/2

48,49,50,50,50,51,52   runs  :  Here n=7, QD = (51-49)/2 = 1

0,25,26,50,50,99,100   runs  : Here n=7, QD = (99-25)/2 = 37

The quartile deviation is a slightly better measure of absolute dispersion than the range. But it ignores the observation on the tails. 

 

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