Rules and Regulations
7. Final Oral Examination
From the graduate school webpage (http://gradschool.princeton.edu/academics/policies/fpo/):
The final public oral examination is a final examination in the student's field of study as well as a defense of the dissertation. The department holds the final public oral examination after the Graduate School reviews and accepts the readers' reports and is satisfied that all other requirements have been met. The department is required to post prominently the date, time, and place of the examination for a minimum of three days (including Saturday) between the dean's authorization and the date of the examination, in order to assure the open, public character of the oral. There are at least three principal examiners, all of them normally members of the Princeton faculty at the rank of assistant professor or higher, at least two of whom have not been principal readers of the dissertation. The department determines whether or not the candidate has passed the examination.
In case the examination is not sustained, the candidate may stand for it a second time after at least one year has passed. If unsuccessful a second time, the candidate is not permitted another opportunity to retake the examination, and Ph.D. candidacy is terminated. In cases where an appearance for the final public oral examination would constitute a substantial financial hardship for the candidate, the director of graduate studies may recommend to the dean of the Graduate School that the examination be waived.
The Final Oral Examination by a faculty committee is a public oral examination in the field of study and shall not be merely a defense of the dissertation, in addition to a defense of the dissertation a candidate is expected to demonstrate a mastery of material broadly related to the thesis topic. The examination committee may be the same membership that has served as the advisory committee after the General Exam, or may be reconstituted as desired at the discretion of the student in consultation with the advisor and advisory committee, with approval by the DGS. In general, The Final Public Oral starts with the candidate giving a talk of about 40 minutes' length on his dissertation research. Next, members of the audience who are not members of the examining committee can ask questions. Then members of the examining committee ask their questions. After this round of questioning is concluded, the Chair of the committee will ask everyone to leave except for the committee members and other Princeton faculty members. Those remaining can then continue to examine the candidate.
In order to encourage graduate students to hear and discuss the results of completed theses it is strongly recommended that students who are near to completion present the results at a departmental seminar prior to the final oral examination. This will assure the Ph.D. candidates ample time to describe the contribution they have made and everyone else the opportunity to ask questions. In addition this will encourage finishing students to prepare a professional seminar on their work, such as might be requested by prospective employers.