The interquartile range (IQR) is a measure of the spread of the data (also called statistical dispersion), ad it’s defined by the difference between the 75th and 25th percentile of the data.
Example Let’s say we need to compute the interquartile range of this dataset:
4,4,10,11,15,7,14,12,6
We first sort it:
4,4,6,7,10,11,12,14,15
The median value is 10. If we take the left part , then the median value is the average between the two center numbers . Same thing on the right side, we take the middle average and we get . So the IQR is .