Comparing simulated and fitted EoR power spectra using Eq. (3). The top panel shows a comparison between the 21 cm signal power spectrum of our fiducial reionization scenario and its best-fit power spectrum obtained using Eq. (3). Different colors represent different redshifts. The lines correspond to the power spectrum ${\mathrm{\Delta }}_{\delta T_{\text{b}}}^2$ from GRIZZLY simulations while the points stand for the fitted power spectrum ${\mathrm{\Delta }}_{\delta T_{\text{b}},f}^2$. The bottom panel shows the percentage fitting error Err$({\mathrm{\Delta }}_{\delta T_{\mathrm{b}}}^2)=(1-\frac{{\mathrm{\Delta }}_{\delta T_{\mathrm{b}},f}^2}{{\mathrm{\Delta }}_{\delta T_{\mathrm{b}}}^2})\times 100\%$.