Answer:
There are three steps to find IQR
1. Know how the IQR is used. Essentially, it is a way of understanding the spread or "dispersion" of a set of numbers. The interquartile range is defined as the difference between the upper quartile (the highest 25%) and the lower quartile (the lowest 25%) of a data set.
2. Understand quartiles. To visualize a quartile, chop a list of numbers into four equal parts. Each of these parts is a "quartile."[2] Consider the set: 1, 2, 3, 4, 5, 6, 7, 8.
1 and 2 are the first quartile, or Q1
3 and 4 are the second quartile, or Q2
5 and 6 are the third quartile, or Q3
7 and 8 are the fourth quartile, or Q4
3. Learn the formula. In order to find the difference between the upper and lower quartile, you'll need to subtract the 25th percentile from the 75th percentile.
The formula is written as: Q3 – Q1 = IQR.