The null-hypothesis in this case is the equality of the SPDs: the sample dates are generated from identically shaped population curves. For example, Collard and colleagues have compared different site types, whilst Stevens and Fuller suggested a failing of Neolithic farming in Britain based on the observed divergence in the SPD obtained from hazelnut/wild plants and cereal/crops. We argue that these types of studies can benefit from a statistical test that can highlight statistically significant differences, as well as provide a global p-value.
We also examined a uniform distribution as an alternative null that does not assume an exponential increase in the underlying population, but instead look for significant deviations from a simpler “flat” model
- 14 C samples of each site of each set are calibrated and aggregated (i.e. a pooled mean is computed) in bins based on prior archaeological knowledge (e.g. same context unit) or chronological proximity (e.g. by site-phase, as in , or ).
- Pooled mean probabilities obtained from bins are summed to generate an empirical SPD for each set.
- The assignment of each bin to a specific set is randomly permuted (so that the total number of bins associated to each set is identical to the observed), and an SPD is generated from each set. Læs videre “Several recent works have relied on the comparison of SPDs”