In our view such usage is often unwieldy, since it can be difficult to make the necessary visual comparisons across a page or even across several pages. Often presentation in a single diagram would be preferable, but histograms are not particularly suited to this. Frequency or cumulative frequency polygons might be used, but the former can be distractingly unsmooth, while the latter can be difficult to interpret by the non-specialist. The smoother nature of a KDE makes it well-suited to comparative presentations, and is illustrated here. Figure 2 compares the distribution of the concentration of calcium oxide for specimens from four sites, using the site numbering from the original paper.
Several features are immediately evident.
The clearly bimodal distribution for site 9 is also associated with larger values, on average, than the other sites. Interpretation of these, and other, patterns is obviously an archaeological rather than statistical problem, but we would argue that the patterns to be interpreted are made much clearer in this sort of diagram than in a collection of histograms. Figure 3 is as Figure 2, but using all those sites for which there is a reasonable amount of data. Readers are invited to draw their own conclusions about the extent to which Figure 3 is comprehensible, and we invite comment on this. If a distribution has a long tail, possibly containing outliers, this can have an undue influence on the KDE, causing it to be biased.