For the Raman spectra, numerical noise does not affect the derivatives of the electronic polarizability when using a step length of δx = 10–3 Å. The numerical anharmonic corrections to the spectral intensities are thus in better agreement with the analytic ones than in the infrared case, but the corrections to the vibrational frequencies remain wrong. Considering the intensities, the numerical spectrum obtained using a step length of δx = 10–3 Å shows differences of less than 10% compared to the analytic spectrum, and is thus in better agreement than the spectrum obtained using a step length of δx = 10–2 Å, where these differences may be as large as 20%. The only exception is the 81 mode, for which both step lengths give corrections that are far from the analytic one. As for the IR spectra, the calculated corrections can be both larger and smaller than the analytic result and whether the corrections are over- or underestimated also depends on the step length. It should also be noted that, depending on the step length used, the ordering of the intensity of the peaks can differ. For example, in the case of δx = 10–2 Å, 11 is slightly more intense than 21, whereas with δx = 10–3 Å, the 21 peak is more intense than 11, in agreement with the analytic differentiation results.