(a) Radio-loud fractions of tQSOs (open blue triangles) and rQSOs (open red squares) with different luminosities. The data points at log(L₄₀₀₀) > 43 can be ignored due to meaningless statistics (small sample size). (b) Radio-loud fractions of tQSOs (open blue triangles) and rQSOs (open red squares) with different redshifts. The symbols are the same as those in the left panel.