Before revision:  In the QR case, the instruments may be relevant at some quantiles but not at others or at the mean . Monte Carlo experiments provide numerical evidence that the proposed tests work as expected in terms of empirical size and power in finite samples.
After revision:  In the QR case, the instruments may be relevant at some quantiles but not at others , which indicates the use of weak-identification robust inference . Monte Carlo experiments provide numerical evidence that the proposed tests work as expected in terms of empirical size and power in finite samples.