The selection by maximum R2 (multiple correlation
coefficient) improvement was used in multiple
regression equations. For one variable, T-EX
was selected, and for two, three, four and five
variables, the combination of T-EX and HA-U;
T-EX, HA-U, and T-U; and T-EX, HA-U, T-U
and CR-U; were selected (Table 3).