A Doctorate of Chiropractic degree is earned from an accredited college and doctors of chiropractic can be licensed primary care doctors. The chiropractic curriculum is extremely rigorous: in fact, chiropractors have more classroom education than medical doctors (4,485 classroom hours compared to 4,248, according to Center for Studies in Health Policy, Inc., Washington, DC. Personal communication of 1995 unpublished data from Meredith Gonyea, Ph.D.). A residency is also completed, where students work with real patients under the guidance and leadership of licensed doctors of chiropractic. Upon completion of school, students must pass four sets of national board exams. There are some states, like Wisconsin, that have a passing requirement higher than the national requirement. Wisconsin also requires 48 hours of additional nutrition classes and testing.