Fig. 6
a and c Box plot comparing the \(\widehat {\beta } _{0}\) values of the classical quantile regression Q R (τ|x) and the weighted quantile regression method Q W(f)(τ|x) to the true β 0=1 (blue solid line) for τ=0.95 and 0.97 respectively. b and d Box plot comparing the \(\widehat {\beta }_{1}\) values of the classical quantile regression Q R (τ|x) and the weighted quantile regression Q W(f)(τ|x) to the true β 1=1.1147 and β 1=1.4026 (blue solid line) for τ=0.95 and 0.97 respectively; Q R (τ|x) - left box plot and Q W(f)(τ|x) - right box plot