Individual fitted Si abundances for a set of eight Si i lines and one Si ii line as a function of equivalent width (left) and excitation potential (right) for eight Si i lines and one Si ii line. Only the Si i lines are used to determine the mean and RMSE (see definition in Eq. (8)), given in the legend in the left panel. G73+OBL91 indicates oscillator strengths from Garz (1973) normalised according to the results of O’Brian & Lawler (1991a); the oscillator strength for the Si ii line for comparison was taken from Kurucz (2014); PR18 indicates oscillator strengths from Pehlivan Rhodin (2018).