Cumulative histograms averaged over 10 000 simulations of X-ray luminosity distributions derived using the CgI model (continuous line) and the steep transition model (dashed line). The distributions of stellar X-ray luminosities around their average values are assumed to be Gaussian with a relative standard deviation of 0.5 (lefthand graph). Relative standard deviations of 1.3 for the C-sequence and the gap stars and of 4.0 for the I sequence are assumed in the righthand graph. The error bars correspond to a ±2σ accuracy. The bold line represents the cumulative histogram of measured X-ray luminosities in M 35.