The interquartile range is the section of data between the lower and upper quartiles, comprising exactly 50% of the data. Much like the regular range, the IQR reflects how spread out a data set is: a lower IQR means that data is clustered closely around the median, while a large IQR suggests the data is more spread out. Understanding the IQR can help illuminate patterns within the data, and help show how reliable the conclusions drawn from a data set are.