ABSTRACT
Statistical methods are based on certain assumptions. For applying parametric statistical tools, the assumptions made are that data follow a normal distribution pattern and are homogeneous. In many situations, the data obtained from animal studies contradict these assumptions, and are not suitable to be analysed with the parametric statistical methods. Non-parametric tests do not require the assumption of normality or the assumption of homogeneity of variance. Hence, these tests are referred to as distribution-free tests. Non-parametric tests usually compare medians rather than means, therefore inÀ uence of one or two outliers in the data is annulled. We shall deal with some of the most commonly used nonparametric tests in toxicology/pharmacology.
