Interaction between numerical variables in regression model, and its graphical interpretation

Background and aim: One of the most important steps in the models to be established in order to define the relationships between the measured characteristics in health field research is to define the effects in the model correctly. One of these effects is the interaction effect, which is rarely used in practice, but on the contrary, should be required frequently used. The aim of this study, the concept of interaction between numerical independent variables, which is rarely used because it is little known in regression-like models, is to be presented with an easily interpretable graphical result.