There is no any single model or method that is perfectable to all other, or that consistently renders the best solutions to public problems.
Policy analysis is one activity for which there can be no fixed program, for policy analysis is synonymous with creativity, which may be stimulated by theory and sharpened by practice, which can be learned but not taught.
In large part, it must be admitted, knowledge is negative. It tells us what we cannot do, where we cannot go, wherein we have been wrong, but not necessarily how to correct thses errors. After all, if current efforts were judged wholly satisfactory, there would be little need for analysis and less for analysts.