Upper panel: the simulation outputs relative to an APEC spectrum with kT = 1−7 keV 100 ks observation extracted from a region size of 0.5 the field of view in a high signal to background ratio regime (SB = 5 × 10^-11 erg s^-1 cm^-2 deg^-2). Different colors indicate the distribution of the results of the fits of different input temperatures (200 realizations each). Middle panel: the same of the upper panel in the case of low signal to background ratio (SB = 5 × 10^-12 erg s^-1 cm^-2 deg^-2). Lower panel: the distribution of the T_i scatter values measured at T_m = 3 keV relative to the two different values of surface brightness; the intervals between 16th and 84th percentile of both distributions are in evidence.