A simple, consistent method is to find the points midway between each end of the range and the median. Thus the mid point lies between 0.8 and 1.1, or 0.95. This is the first quartile. Similarly the third quartile is mid way between 1.9 and 2.0, or 1.95. Thus, the interquartile range is 0.95 to 1.95 .
Data display The simplest way to show data is a dot plot.
Figure 1.3 shows the data from tables 1.2 and 1.3 and together with the median for each set. Figure 1.3 Dot plot of urinary lead concentrations for urban and rural children. If possible the links should be maintained in the display, for example by joining matching individuals in Figure 1.3 . This can lead to a more sensitive way of examining the data. When the data sets are large, plotting individual points can be cumbersome.