Convolution of a log-normal distribution of column densities of Si iiλ1527, randomly generated, with a CoG to a distribution of EWs. We have assumed a distribution with log  (N/cm^-2) = 14.5 ± 1.0 and also a log-normal distribution of particle velocities with log  (b/km s^-1) = 1.1 ± 0.3 (equivalent to 12.6 km s^-1). The red continuous line indicates the CoG using the central b parameter, while the dotted lines are for b values 1-σ above or below. Continuous blue lines mark the distribution of column densities and its corresponding distribution of EWs once convolved with the CoG. The blue dashed line is the EW distribution that would be produced if the CoG would only have a linear regime.