ESTABLISHED CRITERIA AND SELECTED METHODS FOR EVALUATING CROP YIELD MODELS IN THE AgRISTARS PROGRAM

Eight criteria have been established in the AgRISTARS Program to guide the evaluation and comparative analysis of crop yield models. The establishment of these criteria closely corresponds to the spirit of Dr. Hartley's ASA Presidential Address, particularly section three entitled "The Cooperation Between Statistician and Subject Matter Specialist" (1980). In our case the cooperation is between statisticians and two types of subject matter specialists. One type includes commodity specialists or the users of the output of crop yield models as a tool in assembling agricultural intelligence about the production of major crops both in the United States and worldwide. The other type of specialists are those who develop crop yield models or methods of forecasting prospective crop supplies and estimating harvested production (interestingly, most model developers are not statisticians). Because the users of crop yield models are interested primarily in average yields over rather large areas, the criteria to be discussed might seem rather narrow-minded. This is particularly true with respect to the model developers who often develop models capable of generating farm management and alternative production practice advisories. The criteria reflect the users' needs by concentrating on passive (nonintervention) monitoring of the prospective or actual yield. The information developed will, of course, impact on various market adjustments, including international trade.