Find the median. Separate everything above the median into two groups. Take the group with the larger numbers we’ll call this the upper quartile. Find the median of the larger group or upper quartile. Take the group with the smaller numbers, which we’ll call the lower quartile. Find the median of the smaller group or lower quartile. Subtract the median of the lower quartile from the median of the upper quartile and you will find the inner quartile range. In this case, it is 21
