Top left: observed core-separation distribution (solid line) compared with the expected distribution for random distribution of the same number of cores as the observed sample over an identical area (dashed line). Top right: same as in the top left panel but for the nearest-neighbour distribution. Bottom panels: same as in the top panels, but SMM 7, IRAS 05412-0105, and IRAS 05413-0104 have been excluded from the samples.