wherein \(\theta_{i}\) is the cumulative probability that the variant is
placed in the class \(1\leq j\leq i\); \(x_{i1}\), \(x_{i2}\),\(\ldots\), \(x_{\text{iu}}\) are the independent variables that have
some effect on the classification probability, beginning at \(x_{i1}\);
and \(\beta_{1}\), \(\beta_{2}\), \(\ldots\), \(\beta_{u}\) are
regression coefficients, which define the relative weightings placed on
each \(x\) value up to \(u\) independent variables. Thus, equation (1)
may be expanded to the more pragmatic model