Distribution-free range confidence intervals

Estimation of confidence intervals for first or last appearances. Assumes there is no correlation between stratigraphic position and gap size. Section should be continuously sampled. Expects one column per taxon, with levels or dates of all horizons where the taxon is found. This method (Marshall 1994) does not assume random distribution of fossiliferous horizons. It does require that the levels or dates of all horizons containing the taxon are given. The program outputs upper and lower bounds on the lengths of the confidence intervals, using a 95 percent confidence probability, for confidence levels of 50, 80 and 95 percent. Values which cannot be calculated are marked with an asterisk (see Marshall 1994).

Reference

Marshall, C.R. 1994. Confidence intervals on stratigraphic ranges: partial relaxation of the assumption of randomly distributed fossil horizons. Paleobiology 20:459-469.