You can augment a chart for individual measurements with one of several graphical displays, such as a histogram or a box-and-whisker plot. These displays summarize the measurements plotted on the ...

The interquartile range (IQR) is therefore 18 - 4 = 14. You will notice that the fact there is an outlier in this data (60) which has had no bearing on the calculation of the interquartile range.