Population-level comparison between the normalized Hα chromospheric activity index and the spot-modulated photometric-variability scale R_eff. Other MS eruptive stars and RS CVn systems are shown separately, with individual sources color coded by effective temperature. Red lines show descriptive linear fits and the shaded regions show 3σ bootstrap uncertainty bands. No significant relation is detected for the other MS sample (N = 69, slope = −0.01, ρ = 0.05, p = 0.712), whereas the RS CVn subset shows a statistically significant negative rank correlation (N = 37, slope = −0.28, ρ = −0.45, p = 0.005). R_eff is treated as a photometric-variability scale rather than a direct measurement of flare size or starspot radius.