The applicant also may be required to have a personal interview with a representative from the admission's office. After applicants have successfully been enrolled, they may receive a liberal education in most of the universities, which means students are required to take courses across several disciplines before they specialize in a major field of study. Graduate and professional (such as medicine or law) programs are specialized. At the university level, most courses are only one semester long. Each course is assigned a number of credit hours. Credit hours are usually based on how much time is spent in class. Most courses are three credits. However, some courses may be one, two, four or five credits. All degree programs require students to complete a minimum number of credit hours before graduation. Most Bachelor's degree programs in the United States do not require students to write a final thesis. Selection for admission to a graduate program is based on several criteria. These include completion of a Bachelor's degree, the student's undergraduate coursework, and their GPA. Students are also expected to write an essay as part of their application or submit a writing sample.