Mathematics for IGCSE & O level - Statistical Diagrams (Section 3 - No. 24)
If a data set's interquartile range (IQR) is small, this indicates:
The data is widely dispersed.
The data is closely clustered.
The mean is high.
The median is low.
Explication
A smaller IQR indicates that the middle 50% of the data is tightly packed together, hence closely clustered.