This Ph.D. program also offers a terminal master's degree (M.A.) option in experimental psychology and a combined B.A.–M.A. option with a concentration in one of the concentration areas of experimental psychology, human factors. The doctoral program typically takes four to five years of full-time study, and the terminal master's program typically takes two years of full-time study. Graduate students in the human factors concentration frequently complete an approved internship, often for one to two semesters, at an appropriate agency (e.g., federal or state agency, consulting company, engineering group, high-tech business, transportation agency, healthcare facility, military base). The concentration areas available in the experimental psychology graduate program at the master's and doctoral levels are cognitive psychology, human factors, and social psychology. A doctoral degree in psychology has some variance in the required total hours because of such factors as the differences between doctoral psychology programs, diversity of student interests, range of academic backgrounds, and other practical issues. Doctoral students in psychology at Texas Tech typically earn approximately 72-90 credit hours of required coursework in their graduate program before successfully completing their doctoral degree. In addition, other doctoral program requirements must be completed successfully before the doctoral degree is awarded.