what is iqr in statistics

The interquartile range (IQR) is a measure of statistical dispersion, which is the spread of the data. It is defined as the difference between the upper and lower quartiles, Q3 and Q1, respectively. Quartiles segment any distribution that’s ordered from low to high into four equal parts. The IQR contains the second and third quartiles, or the middle half of the data set. The IQR is used to build box plots, simple graphical representations of a probability distribution. The IQR is also useful for datasets with outliers because it’s based on the middle half of the distribution, making it less influenced by extreme values. The IQR can be used to identify outliers and may indicate the skewness of the dataset. The quartile deviation or semi-interquartile range is defined as half the IQR.