In this paper we will test the homoscedasticity of errors using the Goldfeld-Quandt test and we will classify the points using the explanatory variable by which we sort them. We will also use the Hartley test for the equality of the class error variances (if we have at least two classes). For...

In this paper we classify competitive markets using a new form of normalized Herfindahl index and the degree of dominance of the leader. For this purpose we use the notion of copula, which connects two or more random variables with given marginals. The parameters of the two marginals (which are...