Positional offset between the detected sources and the injected sources from the 500 realizations of the estimated underlying counts models (Sect. 4) as a function of the S/N of the detections. The gray dots are ∼100 000 simulated data-points. We show the mean (red) and median (yellow) values of the positional offsets in different S/N bins. The blue dashed curves enclose the 1σ range relative to the mean curve. The test is shown for both 850 (top) and 450 μm (bottom). The dot-dashed black lines indicate the predictions from Ivison et al. (2007) based on the LESS sample.