Optimal designs for estimating model parameters and other characteristics such as mean and median willingness-to-pay are discussed.when a logistic or a probit regression model is used for analyzing a contingent valuation study with discrete questions. A numerical example, related to a study of the value of preserving some virgin forests in Sweden, illustrates the efficiencies of different designs and how a sequential procedure can be applied.

Don Coursey, Hans Nyquist, On Least Absolute Error Estimation of Linear Regression Models With Dependent Stable Residuals, The Review of Economics and Statistics, Vol. 65, No. 4 (Nov., 1983), pp. 687-692