Fuzzy Evaluation on the Validity of System Dynamics Models

Abstract

How to evaluate the validity of the system dynamics models, which is a subject of interest to us. Generally speaking, it is necessary to test the model extensively from different angles, so that people can understand and believe in that model all through, this is so called the validity of the model. Of course, this shouldn’t be all right to evaluate the validity of the whole model only depend on a single test. Hence, the problem is how to evaluate completely the validity of the model through multiple tests. In practice, this is a problem about the synthetical evaluation. The synthetical evaluation can use the approach to find the sum, namely keep the score for the result of each test and then count up them. It can also use the weighted average method. But they aren’t suitable to evaluate the validity of the models. Because the validity is a fuzzy conception. Only using a simple fraction to evaluate the validity of the system dynamics model is not precise. Therefore, it probably is a better method to evaluate the validity of the model synthetically using the fuzzy sets theory. This paper discusses the multilevel evaluation system and fuzzy synthetical evaluation method for the validity of the system dynamics model, and gives a computation example at last. The example proves that fuzzy synthetical evaluation can give satisfactory results.