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The Calculation of LD50 Using Probit Analysis
Author(s) -
Akçay Aytaç
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.1217.28
Subject(s) - probit model , probit , statistics , regression analysis , negative binomial distribution , linear regression , population , mathematics , econometrics , computer science , medicine , environmental health , poisson distribution
Probit analysis is a type of regression used to analyze binomial response variables. The statistical theory and techniques using probit analysis for analyzing data from dose‐quantal response experiments were developed by D.J. Finney (1971) and details are discussed in Finney (1978) and Robertson et al (2007). Data obtained from the bioassays are generally in percent response (mortality or affected) at the corresponding doses (or concentrations). The response is always binomial (e.g. death/no death) and the relationship between the response and the various concentrations is always sigmoid. Probit analysis acts as a transformation from sigmoid to linear and then runs a regression on the relationship. Once a regression is run, the researcher can use the output of the probit analysis to compare the amount of chemical required to create the same response in each of the various chemicals. There are many endpoints used to compare the differences of doses response, but LD50 are the most widely used outcomes of the modern dose‐response experiments. LD50 represent dose at which 50 % of the population responds. The critical LD50 values may be estimated from probits and log doses in several ways. The simplest is by graphical methods. Another is by using standard computation using a calculator (Finney 1971, Heong 1998). Step by step calculations are also available in Busvine (1971). The faster and more accurate way is using computer program or software. Several statistical packages like SAS, SPSS, R, Statistica etc. have probit analyses options. Aim of this study, to introduce the application of software SPSS 14.01 in calculation of LD50. The parameter estimates, probit analysis and graphs in probit transformed responses were output automatically. As a result, the calculation of LD 50 using Probit Analysis with SPSS is simple, rapid, visual and convenient.