Bayesian decision theory Under continuous feature x we have observed, assume ${\omega_1, \omega_2, ...\omega_c}$ ... $c$ finite categories ${\alpha_1, \alpha_2, ...\alpha_a}$ ... $a$ finite possible actions then loss function $\lambda(\alpha_i \vert \omega_j)$ ... the loss caused by taking an action $\alpha_i$ when $|omega=j$ is the situation. see paper -> likelihood ratio two-category classification => discriminant function