Moreover, paradigm goals and contexts may change during the planning process with the result that what was originally thought to be feasible and desirable is no longer, and vice versa. Thus, for any paradigm implementation, flexibility is important. This means that paradigm implementation should be de-signed so that strategies can be changed if circumstances demand it. In general, evaluation plans should include the identification of evaluators, evaluation criteria, evaluation methods, evaluation timing, and potential evaluation obstacles. Even when evaluation is done well neither the means nor the ends may be justifiable.
Good evaluation is costly.
It requires highly trained talent, money, and time. In addition, not all paradigms are important enough to warrant extensive evaluation. Moreover, the decision to evaluate is all the more difficult given the fact that by their nature evaluations disrupt, reveal institutional weaknesses and limitations, and threaten individual policies and their sponsors. Nevertheless, paradigm evaluation is necessary if paradigms are to be improved. Thus, obstacles to policy evaluation must be identified and overcome.