Final answer:
In the executive branch, individual departments and agencies are responsible for policy analysis and implementation. Experts within each agency evaluate proposal impacts and the bureaucracy details how federal polices, regulations, and programs will be implemented.
Step-by-step explanation:
In the executive branch, each individual department and agency is technically responsible for its own policy analysis. The assumption is that experts in the Federal Communications Commission or the Federal Elections Commission are best equipped to evaluate the impact of various proposals within their policy domain. Law requires that most regulatory changes made by the federal government also include the opportunity for public input so the government can both gauge public opinion and seek outside perspectives.
Once the particulars of implementation have been spelled out in the legislation authorizing a new program, bureaucracies move to enact it. When they encounter grey areas, many follow the federal negotiated rulemaking process to propose a solution, that is, detailing how particular new federal polices, regulations, and/or programs will be implemented in the agencies. Congress cannot possibly legislate on that level of detail, so the experts in the bureaucracy do so.