Abstract

Existing methods for point and interval estimation of the endpoints of the stratigraphic range of a fossil taxon under continuous sampling assume that the mean density of finds is constant over the stratigraphic range. These methods can perform badly when this mean density is not constant. Most seriously, if mean density declines toward the endpoint of interest, then the true coverage of the confidence interval for the true endpoint can be far below its nominal level, giving a false impression of estimation precision. Simple point and interval estimates that are designed to avoid this problem are presented. These methods are illustrated with the fossil record of two species of the Caribbean bryozoan Metrarabdotos.

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