Normalized sample covariance between mass bins from simulations (top) and our analytical model (center), computed for 10⁶ spherical sub-boxes of radius R = 200 h⁻¹ Mpc at redshift z = 0.506 and in the mass range of 10¹⁴ ≤ M/M_⊙ ≤ 10¹⁶. Bottom panel: relative difference between simulations and model for the diagonal elements of the sample covariance matrix (blue) and for the shot-noise (red).