Before revision:   Our proposed technique is a practical alternative to standard NPIV estimation and allows the researcher to make meaningful inferences about the structural function when  misspecification cannot ruled out.
After revision:  The set estimator can interpreted as error bounds on a point estimator and used to perform sensitivity analysis. Our proposed technique is a practical alternative to standard NPIV estimation and allows the researcher to make meaningful inferences about the structural function when misspecification cannot ruled out.