Table 4. Values of the Estimates of the Concentrations of Propofol and Alfentanil Associated with a 50% Probability of No Response (EC50Prop, EC50Alf), epsilon, the Residual Sum of Squares (RSS), and the Correlation Coefficients (R2) for the Two Possible Interactions (Additivity or Nonadditivity) for Loss of Eyelash Reflex and Loss of Consciousness