Scattering time vs. DM_EG or DM_h. The x-axis is the DM_EG from Eq. (12) in the log scale for the FRB samples (black dots), and it shows DM_h for the empirical relation based on Galactic pulsars (shaded blue region) and the $A_{\tau }\stackrel{\sim }{F}G$ models (solid colored lines). The y-axis is the scattering time at the rest-frame frequency of 1 GHz in the log scale. The black points are the 30 FRBs in our work. The pink circles are the $A_{\tau }\stackrel{\sim }{F}G$ outliers in our FRB samples. The orange circle is one of our FRB samples, which is DM_IGM < 0 pc cm⁻³. The colored lines are the $A_{\tau }\stackrel{\sim }{F}G$ models from Eq. (3) with DM_h = [20, 1600] pc cm⁻³. The blue area is the empirical relation derived from Galactic pulsars described in Eq. (13), which includes the geometrical scaling factor for the FRB samples.