The function defined by

where

and is the th derivative of .

**References**

Kenney, J. F. and Keeping, E. S. ``Tetrachoric Correlation.'' §8.5 in *Mathematics of Statistics, Pt. 2, 2nd ed.*
Princeton, NJ: Van Nostrand, pp. 205-207, 1951.

© 1996-9

1999-05-26