A Study of Sensitive Test

It is necessary to test a newly built model to make sure that it does simulate the actual system. The test may include many aspects, such as sensitive test, comparison test with history data, etc. This paper studies sensitive test and presents some result of the findings.In studying the structure of a given system, the endogenous variables and exogenous variables are given explicitly. If we can not tell the difference between them correctly, it may confuse the real meaning of the sensitive test.In the present analysis we find that the conditions for non-sensitivity of variables to a model are: 1) the change is made for one variable only and 2) the change is small. The conditions for sensitivity of variables to a model are: 1) two or more variables change at the same time and 2) the change is great. A model may also become sensitive for a small change of the exogenous variable.The above results have been thoroughly investigated and the methods of sensitive test are presented.The system always changes from one stable condition to another stable condition in which it is non-sensitive to variable changes, but if the system is in a state between two stable conditions, it is completely possible to become sensitive to variable changes. So we may point out that the model builder and analyst are required to find out the correct boundary of stable conditions.Finally, the simple economic long wave model is tested to confirm the above results.Recent evidence (System Dynamics Review vol.4, No.1–2, 1988) points chaotic modes do exist in the range of models commonly explored by most students and practitioners of System Dynamics. Experiments also demonstrated that chaos can in fact be produced by decision-making processes of real people. Chaos thus appears to be a common mode of behavior not only in physical systems, but also in social and economic systems. However, chaos is a steady-state pheonomena over very long time frame and many policy-oriented models are concerned with transient dynamics with time horizon much shorter than those used in chaotic dynamics. Over such extended time horizons the parameters of the system can’t be considered static, but will themselves evolve with learning and evolutionary processes.With such a viewpoint in mind we have explored a study of sensitive test in the following way.