在这篇文章的第9页，有一个敏感性分析

Figure 1.
Sensitivity analysis with continuous outcome and mediator. Figure 1A is for the estimated average mediation effect under the control, and Figure 1B is for treatment. The dashed line represents the estimated mediation effect for[size=10.6667px]ρ=0. The gray areas represent the 95% confifidence interval for the mediation effects at each value of [size=10.6667px]ρ. The solid line represents the estimated average mediation effect at different values of[size=10.6667px]ρ.


这里的ρ怎么解释，谢谢！