rms of the Landy-Szalay estimator for lognormal simulations in a cubic geometry and for a zero two-point correlation function (left) and for a ΛCDM model (right). The upper, middle, and lower solid lines correspond to a random sample with 1, 3, and 30 times more galaxies, respectively than the data sample. Dotted lines show the Poisson noise associated with each number of randoms (in the same order as solid lines). The thick dashed line shows the limit corresponding to an infinite number of random galaxies. (Coloured version of the figure available online.)