18.2 Key Terminology

• Main Effect: The effect of an independent variable without considering interactions.
• Interaction Effect: The combined effect of $X$ and $M$ on $Y$.
• Simple Slope: The slope of $X$ on $Y$ at a specific value of $M$ (used when $M$ is continuous).
• Simple Effect: The effect of $X$ on $Y$ at a particular level of $M$ when $X$ is categorical.