An interactive computer program that accurately estimates the ED50, its standard error and other parameters related to the probit regression line.

A program suitable for terminal, conversational-mode usage was developed in the BASIC language to compute the median effective dose (LD50), various error terms, and confidence intervals. The overall algorithm used in the program was based on a method described by Finney. The accuracy, speed and flexibility of the program makes the terminal approach an efficient alternative to simple graphic methods.