The study of public policy and political science overlap considerably, though their differences are equally significant. While a Ph.D. in public policy is an applied interdisciplinary science that utilizes tools from political science, economics and sociology, a Ph.D. in political science is much more theoretical. While this is the primary difference, programs vary by school, and in many cases the two Ph.D.s look quite similar.

Differences in Admissions

While the differences in admissions between a Ph.D. in public policy and one in political science are not absolute, differences do occur. Most frequently, public policy programs will expect some sort of work experience, either in the public sector or in research. Duke's Sanford School, for example, says this experience is strongly encouraged. The Ph.D. program in political science at Duke, however, makes no mention of work experience, and this difference in admissions policy appears at similar universities. Additionally, unlike political science programs, Ph.D.s in public policy typically prefer students who already hold a master's degree while political science programs will take bachelor's-only students.

Course Work Differences

The curricula of political science and public policy Ph.D. programs is where the two fields differ most. While both degrees likely require some quantitative preparation, the math requirements for a public policy degree will be much more rigorous. In the case of Harvard University, for example, the political science degree merely requires one course in quantitative methods, while the public policy Ph.D. requires nothing less than multivariate calculus. This is because a degree in public policy focuses on the analysis of specific policies, while political science is more theoretical and thus does not necessarily require as much math.

Differences in Thesis or Dissertation Topics

Like the required courses for each program, the type of research conducted within each also varies. For policy Ph.D. candidates, research likely involves an applied, specific topic. At Harvard University, recent dissertation titles include "Essays on Child Mortality and Growth Faltering in Bangladesh and Kenya" and "Responding to Risk: Information and Decision Making in the Floodplains of St. Louis County, Missouri." At Duke University's political science program, however, titles are much less specific, and include topics like "International Crises, Armed Non-State Actors and Crisis Violence," and "Toward a Theory of Civil-Military Punishment." For political science programs, research is much broader and global in scope than a public policy Ph.D.

Post-Ph.D. Employment Placements

The final major difference between the political science Ph.D. and the public policy Ph.D. involves career paths after graduation. For political science students, post-graduation jobs are almost always in academia. In the case of Duke University, 90 percent of graduates work as professors at colleges and universities. Public policy Ph.D.s, on the other hand, do not necessarily work in academia. Many work in government, non-profits or private industry, conducting research on policy.