Abstract: Binary Similarity Coefficients and Confidence Intervals

William W. Hay, John R. Southam

Binary similarity coefficients are used in stratigraphy, paleontology, and taxonomy to express similarity between data sets. They have been used in comparing assemblages of fossils for both stratigraphic correlation and paleoecologic interpretation. Although many coefficients have been proposed, only five are common in biostratigraphic work: the Jaccard, Dice, Simpson, Fager, and Otsuka. The problem with all of these coefficients is that they are sensitive only to the relative, not the absolute, size of two samples. More meaningful coefficients can be developed by including the width of the confidence interval ^dgr for the appropriate proportions as a part of the expression. Confidence intervals can be formulated on the basis of the presence or absence of a species in a s ite of sections. Such a situation is appropriately described by a binomial distribution for which the writers previously have calculated confidence intervals.

AAPG Search and Discovery Article #90961©1978 AAPG Annual Convention and Exhibition, Oklahoma City, Oklahoma