Generally, a doctorate degree takes about four years to earn, depending on the program and the school. Many Ph.D. students, called "doctoral candidates," have previously earned a master's degree in the same field, though it is not always a requirement. Usually the Ph.D. degree involves two years of coursework, one year of focused research and one year of work on a dissertation, or final project. Though the criteria varies from school to school, most doctoral degrees require at least 90 hours of collegiate course work, and some require up to 120 hours, which is the equivalent of about 30 to 50 college courses.
Very few careers require a doctorate degree. One of the most common is a college professor. Many four-year accredited colleges require their tenure-track professors to hold a Ph.D. in their field of study. Most states require licensed psychologists to hold a Ph.D. in psychology to practice. Some engineering jobs also require a doctorate degree in engineering. Ph.D.-required positions, such as governmental positions, are often high paying due to the level of experience required to earn this degree.
To apply for a Ph.D. program, a student must have completed his bachelor's degree and, many times, a master's degree as well. Some schools offer a program in which a master's degree can be earned during the student's work towards his doctorate degree. Students must have competitive grades in their field of study, letters of recommendation from former professors and/or employers and competitive scores on either the Graduate Records Examinations (GRE) exam or, for most programs, the GRE subject exam, a comprehensive examination covering the student's desired field of study. Students must also turn in a "statement of purpose" in which they outline their academic and career goals and explain why they wish to pursue a doctorate degree.
The final year of doctorate study often involves the completion of a dissertation, or specialized academic paper that outlines the candidate's final project. For example, if the student is earning a Ph.D. in literature, his dissertation will be a book-length study on a particular author, genre or era. Often, dissertations are later published by academic presses and serve as the student's first major publication within his field of study. The research and writing of the dissertation can take a long time. Once it is complete, there is often a "dissertation defense" in which the student presents his paper to professors at his school and answers a series of questions about it.