Table 2. The Fitted Values of the Coefficients plus/minus Standard Error (SE) of the Two Logistic Regressions That Were Performed to Explore the Possibilities of an Additive and of a Nonadditive Interaction between Propofol and Alfentanil for the Suppression of Responses to Laryngoscopy, Intubation, the Opening of the Peritoneum, and for Awakening, and Their Correlation Coefficients