TETRA - A FORTRAN-IV PROGRAM FOR COMPUTING THE COSINE-PI APPROXIMATION TO THE TETRACHORIC CORRELATION-COEFFICIENT

Research design features relating to the use of a binary response format to measure a continuous latent variable and to the arbitrary dichotomization of graduated data are discussed in connection with the advantages and disadvantages inherent in the use of the tetrachoric correlation. A FORTRAN IV program for computing the cosine-pi approximation to the tetrachoric correlation is described, and the nature and extent of systematic error found in that approximation are summarized.