Ensemble-averaged [Cii] line centre intensities for different realisations of the test ensemble. The circles show the ensemble-averaged intensities of 20 different small intensity maps and the squares give the values for ten different large intensity maps as presented in Fig. A.1. The black line gives the mean value of the 30 maps, weighted by the respective number of grid points. For the 20 small maps the average is (2.24 ± 0.50) K and for the ten large maps it is (2.17 ± 0.33) K. The stated error is the standard deviation, which, as expected, is larger for the smaller maps. The red, dashed line gives the value derived using the probabilistic approach for the same ensemble. The difference between the two approaches is about 2.6%.