Two Computer Programs for Probit Analysis

Abstract

A statistical technique called “probit analysis” to aid in the interpretation of dose-mortality data has become common practice, not only among entomologists but also among other biologists conducting tests that involve dose and response when the response is quantal. An adequate summarization of dose-mortality data consists of the LD50, its confidence (fiducial) limits, and the slope of the probit regression line or that dose which will cause 50% of the population to respond (die) and the standard deviate of the distribution of tolerances (reciprocal of the slope). However, in practice, the tedious, extensive, and often baffling calculations associated with probit analysis have deterred many biologists from obtaining an adequate summarization of dose-mortality data. The increasing number and availability of electronic computers and their ability to process routinely large volumes of calculations present the biologist with the opportunity of obtaining a much more adequate summary of his dose-mortality data.