Doctor of Philosophy (PhD)

Students intending to pursue the degree of Doctor of Philosophy (PhD) enter our program with Bachelor’s degrees and Master’s degrees from a variety of disciplines. Students entering the PhD program with less background in statistical methods and theory than what is provided by our core Master of Science in Statistics program are advised to take courses from the MS core to prepare for PhD-level study. In addition to the prerequisites listed on the MS Requirements page, we strongly recommend at least one semester of real analysis.

The PhD degree requires 72 credits beyond the Bachelor’s degree, with at least half of those, including all research credits, earned from Iowa State. In addition to the PhD core courses, the Program of Study must include at least four 500- or 600-level statistics courses, with at least two of those at the 600 level and selected from an approved list of 600-level electives. The 72 total credits should include at least 18 hours of research. Students take a written preliminary examination, an oral preliminary examination, write a dissertation containing original research in statistics, and pass a final oral examination.

Learning Goals: Doctor of Philosophy in Statistics

Demonstrate comprehensive understanding of advanced statistical methods and theory, including probability, mathematical statistics, and the construction of probability-based models for complex data structures.
Demonstrate the ability to formulate statistical questions on the basis of objectives in substantive scientific investigations, and the ability to compute the quantities needed to bring statistical theory and methods to bear on those questions.
Conduct original research into one or more specific areas of statistical science that is of sufficient depth to merit publication in a statistical or scientific journal.
Demonstrate understanding of the scholarly literature in the area of dissertation research.
Demonstrate the ability to communicate research results to scientists and other researchers in both written and oral formats.

Core Courses

All students seeking the PhD degree in Statistics are required to know the material in the core courses (STAT 601, 641, 642, & 643). It is assumed that the material in the MS core courses has also been mastered. Many students entering the program with a Bachelor’s degree complete the MS core program in the first year and begin the PhD core in their second year of study. A typical schedule is shown below, and this can be compared to the sample schedule presented for the MS program to see how the PhD core courses would fit into the overall schedule of courses.

Typical Schedule for a Student Entering with a Bachelor’s Degree

Year 1/Fall
STAT 500 (4 cr.) Statistical Methods I
STAT 542 (4 cr.) Theory of Probability and Statistics I.
STAT 579 (1 cr.) An Introduction to R.

Year 1/Spring
STAT 510 (3 cr.) Statistical Methods II
STAT 543 (3 cr.) Theory of Probability and Statistics II.
STAT Elective (3 cr.)

Year 2/Fall
STAT 520 (3 cr). Statistical Methods III
STAT 641 (3 cr.) Foundations of Probability Theory
STAT Electives (3 cr.)

Year 2/Spring
STAT 601 (3 cr.) Advanced Statistical Methods
STAT 642 (3 cr.) Advanced Probability Theory
STAT Electives (3 cr.)

Year 3/Fall
STAT 643 (3 cr.) Advanced Theory of Statistical Inference
STAT Electives (3-6 cr.)

The Director of Graduate Studies and/or Chair of the Department are available to advise a student entering the program with more experience than typically represented by a Bachelor’s degree on how best to sequence core courses and where to begin in the program. If a student enters the program with a Master’s degree in statistics, he or she may be advised to start directly with the PhD core courses or may be advised to include some MS core courses in the first one or two semesters of study.

Alternative Possible Schedule for a Student Entering with a Master’s Degree in Statistics

Year 1/Fall
STAT 520 (3 cr.) Statistical Methods III (optional)
STAT 641 (3 cr.) Foundations of Probability Theory
STAT Electives (3 cr.)

Year 1/Spring
STAT 642 (3 cr.) Advanced Probability Theory
STAT 601 (3 cr.) Advanced Statistical Methods
STAT Electives (3 cr.)

Year 2/Fall
STAT 643 (3 cr.) Advanced Theory of Statistical Inference
STAT Electives (3-6 cr.)

See all courses offered by the department

If English is not a student’s native language, he or she will be required to take an English Placement Test at the start of the first semester of graduate study. Based on the results of this exam, the student may be required to take one or more English courses. Other language requirements, if any, will be established by the Program of Study Committee and major professor.

Written Preliminary Examination

All students seeking a PhD degree must pass a written preliminary examination, which is presently given over three days and covers material from both the MS and PhD core courses. The exam is administered in two parts, one part covering primarily statistical methods and applications (STAT 500, 510, 520, & 601) and one part covering primarily statistical theory (STAT 542, 543, 641, & 642). Note that STAT 643, “Advanced Theory of Statistical Inference” is a required course but is not included on the written preliminary exam. This is because the exam is typically given during the summer, after a student entering with a Bachelor’s degree has completed two years of study and a student entering with a Master’s degree has completed one year of study. Both parts of the written preliminary exam must be taken at the same time. The possible outcomes are: a student may pass; fail but be given an invitation to re-take the exam in the next year; or fail and be asked to find another academic program or institution at which to continue study, if that is desired.

The PhD written preliminary examination is intended to provide both the student and the program with a concrete indication of whether pursuit of a PhD in Statistics at Iowa State is a good option for the student. It serves as a solid indication of whether it will be wise for a student to devote the immense amount of time and energy needed to write and defend a dissertation.

Major Professor and Program of Study Committee

The selection of a major professor is an important milestone in most PhD programs, and often occurs after one or two years of study, when a student has gained some familiarity with the research areas of faculty members in the department. The major professor serves as the principal mentor of a PhD student; provides advice on the selection of elective courses; supervises and advises the dissertation research and preparation of the written dissertation; and assists in nearly every other step of the PhD program. Most students reach agreement with a faculty member to serve as their major professor either the semester before or the semester following the written preliminary examination. Before a major professor has been determined, the student can seek advice from the Director of Graduate Education or the Department Chair.

Along with the major professor, the student selects at least four more faculty members to form a Program of Study Committee, and obtains agreement from those faculty members to participate in the committee. At least one member of the committee must have a primary area of research activity that differs substantially from the topic of the dissertation research. It is common, but not required, that one member of the committee is a faculty member in a department other than Statistics.

The Program of Study Committee conducts the oral preliminary examination and the final oral examination, and approves the official Program of Study, which is a list of coursework that the student will apply toward the PhD degree. The Program of Study serves as an official contract between the student, and the university that the courses listed will satisfy the requirements for core courses, suitable electives, research credits. and total credits. It must be approved by the major professor, committee members, Director of Graduate Education, and the Graduate College.

Dissertation

To be awarded the degree of Doctor of Philosophy in Statistics, a student must complete an original research project that results in a written PhD dissertation. This work will be mentored and directed by the student’s major professor, a faculty member with whom the student reaches a mutual agreement for supervision of the dissertation research project. Although there is no formal requirement for publication, it is typically expected that a dissertation project will result in publishable research, usually in the form of one or more articles in peer-reviewed journals, although such articles need not have been accepted or even submitted for publication at the time a PhD candidate defends his or her dissertation.

Oral Preliminary Examination

After a suitable amount of work has been conducted on the dissertation research project, as mutually determined by the student and his or her major professor, the student requests permission from the Graduate College to take their oral preliminary examination. The oral preliminary exam is conducted by the student’s Program of Study committee, and usually centers on early results from the dissertation research as well as proposed work to be done during the remainder of the student’s program. An important objective of the oral preliminary exam is for the student, the major professor, and the members of the committee to reach agreement on what will constitute an acceptable dissertation for defense at the final oral examination (sometimes called the dissertation defense). When a student passes the oral preliminary exam he or she officially is recognized as a candidate for the PhD degree by the Graduate College.

Maintaining Academic Standing

Students must maintain a 3.0 (B) average to remain a candidate for a degree. Failure to do this can result in being placed on academic probation. Academic probation can have implications for tuition scholarships and require additional permission to allow registration in subsequent semesters. A student cannot receive a graduate degree without removing academic probation by achieving an overall grade point average of 3.0 or higher. Students who fail to reach a 3.0 average during their first semester of graduate study are given a one semester grace period to improve their grades before being placed on academic probation. Failure to raise a grade point average to 3.0 and remove academic probation for two years may be considered failure to make satisfactory academic progress, and result in the termination of an assistantship or membership in an academic program.

Final Oral Examination

When the student and his or her major professor believe the dissertation has reached its final form, and that any concerns or issues raised during the oral preliminary examination have been appropriately addressed, the student schedules and completes the final oral examination or dissertation defense. As part of this examination, the student must present a public seminar concerning the dissertation research. There is then a longer session involving only the student and his or her Program of Study Committee, during which the student presents additional material from the dissertation and answers questions posed by the members of the committee. Passing the final oral exam is the last step in the progression toward completing a PhD degree.

Funding

Almost all PhD students receive funding as a research or teaching assistant and receive a stipend. Our stipend is $2346 per month for a halftime (20 hours per week) assistantship. Funded graduate students also receive fringe benefits including health insurance. Funded PhD students working 20 hours per week receive a full-tuition scholarship.