premise: The newly deployed ground-based mid-course missile defence system comprises 10 interceptor missiles, each of which is intended to collide in outer space with an incoming hostile missile. So far in field trials the system has successfully intercepted target missiles in five out of eight flight tests. Critics say that these trials prove very little. Live tests are very expensive, take a great deal of organization and are usually limited by concerns over safety (you really do not want one of these missiles going astray and crashing into a city centre, for example). For these reasons, a lot of the development programme has relied on models and simulations rather than real flight tests. Both critics and supporters of the programme accept that these models do a far better job of predicting the performance of system components than of predicting the performance of the system overall.
hypothesis: Simulation and theoretical models cannot capture all the variables that can occur in a real missile engagement.