Surface lithic scatters often pose problems for archaeological interpretation because temporally different occupations cannot be distinguished stratigraphically. When composed primarily of obsidian, however, the occupational history of a lithic scatter can be assessed upon analysis of its hydration measurements. A sample of hydration measurements drawn from the scatter are visually displayed using box and whisker plots, and analyzed using two inferential procedures (the W test for normality and Chauvenet's criterion) designed to test whether or not the sample is drawn from a single population. Application of the inferential procedures relies on assumptions about the hydration phenomena. This analysis provides a visual and objective means to decide whether a population of obsidian artifacts was created over a short span of time, or during more than one discrete occupational episode.
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