A computer program for estimating thresholds by means of Wetherill's Up-Down Transformed Response Rule (UDTR)

A Fortran IV computer program is presented which allows for automatic estimation of thresholds on an S-shaped psychometric curve by means of Wetherill's Up-Down Transformed Response Rule (UDTR). The efficiency and asymptotic properties of these rules are discussed and illustrated. The main program is in the form of a keyboard portable tutorial which calls the main decision-making subroutine. The subroutine can be detached from the tutorial. Only a single call with seven parameters is required to reach the subroutine. The program is particularly useful in forced-choice procedures.