Fig. 2

Illustration of different regression models. The Figure illustrates the relationship between a continuous predictor and an outcome variable depending on whether the regression model only comprises the continuous predictor (Example 1), the continuous predictor and the binary group variable (Example 2), or the continuous predictor, the binary group variable and their interaction term (Example 3). The solid line indicates the relationship in the experimental group. The dotted line indicates the relationship in the control group, and the dashed line represents the relationship regardless of the group assignment