Journal of Environmental Biology

Statistical tools for analysing the data obtained from repeated dose toxicity

studies with rodents: A comparison of the statistical tools used

in Japan with that of used in other countries

Author Details

Katsumi Kobayashi (Corresponding author)

National Institute of Technology and Evaluation (NITE), 2-49-10 Nishihara, Shibuya-ku,

Tokyo - 151 0066, Japan

e-mail: kobayashi@beige.plala.or.jp

K. Sadasivan Pillai^???

Frontier Lifeline, International Centre for Cardio-Thoracic and Vascular Diseases,

Chennai - 600 101, India

Soma Guhatakurta

Frontier Lifeline, International Centre for Cardio-Thoracic and Vascular Diseases,

Chennai - 600 101, India

K.M. Cherian

Frontier Lifeline, International Centre for Cardio-Thoracic and Vascular Diseases,

Chennai - 600 101, India

Mariko Ohnishi

National Institute of Technology and Evaluation (NITE), 2-49-10 Nishihara, Shibuya-ku,

Tokyo 151-0066, Japan

Publication Data

Paper received:

01 December 2009

Revised received:

April 24 2010

Accepted:

11 May 2010

Abstract

In the present study, an attempt was made to compare the statistical tools used for analysing the data of repeated dose toxicity studies with rodents conducted in 45 countries, with that of Japan. The study revealed that there was no congruence among the countries in the use of statistical tools for analysing the data obtained from the above studies. For example, to analyse the data obtained from repeated dose toxicity studies with rodents, Scheff?s multiple range and Dunnett type (joint type Dunnett) tests are commonly used in Japan, but in other countries use of these statistical tools is not so common. However, statistical techniques used for testing the above data for homogeneity of variance and inter-group comparisons do not differ much between Japan and other countries. In Japan, the data are generally not tested for normality and the same is true with the most of the countries investigated. In the present investigation, out of 127 studies examined, data of only 6 studies were analysed for both homogeneity of variance and normal distribution. For examining homogeneity of variance, we propose Levene?s test, since the commonly used Bartlett?s test may show heterogeneity in variance in all the groups, if a slight heterogeneity in variance is seen any one of the groups. We suggest the data may be examined for both homogeneity of variance and normal distribution. For the data of the groups that do not show heterogeneity of variance, to find the significant difference among the groups, we recommend Dunnett?s test, and for those show heterogeneity of variance, we recommend Steel?s test.

Key words

Statistical tools, Toxicity study, Rodents, Cluster analysis, Dunnett?s test, Steel?s test

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