Upper: grey dotted lines show the power spectrum measured in each of the 20 fake galaxy distributions, the black solid line represent their average and the errors display the dispersion of the measurements. The blue long dashed line displays the input power spectrum used too generate the Gaussian stochastic field nu and the red dashed line shows the corresponding expectation value for the power spectrum of the density contrast δ. Lower: shows the deviation between the measured power spectrum of the δ-field and the expected one.