Calculation of Inter-Quartile Range (IQR)

The inter-quartile range is the range in which the middle 50% of the data points fall (i.e. the distance between the 1st and 3rd quartile) and would be calculated as follows for the above data set: 25% of n = 25% x (n+1) = 0.25 x 9 = 2.25. Therefore the 1st quartile lies between the 2nd and 3rd lowest observations (i.e. 3 &4). ................
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