Friday, January 21, 2011

Anatomy of a PhD Defense

I remember the first time I went to a PhD defense. I had just finished my first semester as a grad student, and I still had no idea how the graduate student culture worked. I had no idea what to expect during a doctoral dissertation defense.

Now, I'm old and cynical. I started to lose track of the people I knew that had graduated, so now I keep a list of defenses I have attended. This morning, I attended my tenth defense. (I have more friends that have graduated, but sometimes I can't make it to the actual event.)

I was walking over to the room this morning with two first-year grad students. Today was the first defense THEY had ever attended. I started to explain the typical procedures, and I just had a clear sense of time marching on. All things turn over, all new things become old and then new again...

Man, I really am getting old.

But one of the benefits of age is also (hopefully) wisdom. And if not wisdom, at least the ability to draw comparisons. I've seen a fairly wide range of things happen at defenses. :) So I thought I would describe a typical defense, at least as it works in Mechanical Engineering at World's Best School.


First, let's get one thing straight. You KNOW you are going to pass. Your committee of advisors won't let you set a defend date unless you are ready. You can be positive that you'll get a check on your thesis card at the end of the day. But you would like to feel that you nailed the presentation, that you handled all the questions with authority and grace, and that you truly earned your degree. Really, you are fighting for the "Check Plus" instead of the "Check".

Figure: But let's be honest. You wouldn't be at World's Best School unless you always fight for the Check Plus.
So you will probably stress about it anyway. My lab has a student seminar series, run by the students, for the students. Students volunteer to present their work, sometimes to ask for help with their research, but most often in preparation for a) a conference talk b) the qualifying exam presentation, or c) a defense. So often, you will give your presentation to the students first, so that you feel confident on defense day.

The choice of classroom to defend in is also key. If you choose a room in the main engineering building, you are liable to get a lot of random professors "dropping in" to listen. "Drop-ins" tend to ask questions. Hard questions. Off-the-wall questions. Questions you are not prepared for. You don't want drop-ins. :) So it is in your best interests to pick a room that is off the beaten path. Ditto for the time and day (Friday afternoons, everybody is looking for something not-work-related to do... so Monday at 9am is much better), but you don't have much control over that. It's hard enough to get your three committee professors to all have an hour and a half free to slot you in!

The Introduction

On the day of your defense, your advisor will give you an introduction. Some advisors just say, "Here is my student. They have done well. Student, please begin." But it is more common, and a nice touch, for your advisor to introduce you with a quick review of your graduate career, and perhaps an anecdote or two. For instance, one professor recalled the time that his student set the lab on fire. "Despite which," the professor was quick to add, "I am pleased to announce that subsequent experiments fared much better."

Who Attends

The only people who MUST attend are your committee members. Although this morning, one of the committee members had to video conference in from Japan. And another time, the student's actual advisor wasn't even in the room - he had to Skype in from California! That instance was actually the most extreme case I know - that student had three very hard-to-schedule committee members. They were always traveling, or teaching, or otherwise busy. So even after three separate committee meetings, and the defense, he NEVER had all three people physically in the same room. Now that, my friends, is talent.

In addition, anyone at the university is allowed to attend, and the defense announcement is sent department-wide. (See note on choosing classrooms to avoid too many drop-ins...) So your classmates, your friends, and any student who saw the announcement and found it relevant (or who wants to procrastinate from research) will be there.

And usually (excepting matters of national security) the event is open the the public as well. So your family, girlfriend, or anyone else you can convince to sit through a detailed technical presentation can be there as well. In one case, a very popular social student had an entire cheerleading section at his defense. They actually brought little cardboard cutouts, of a "D" and a white picket fence. (Get it? D! Fence!) That, for the record, I thought was a bit unprofessional...

Finally, there may be students who were your friends and graduated ahead of you. It's actually kind of a mini-reunion at some defenses, with alums coming back to support and congratulate you. Again with the sense of time marching on... the world continually turns. :)


Generally the presentation is in PowerPoint, but I saw one student do his using a presentation class of LaTeX called Beamer. If you don't know what TeX is, or you do but you wish you didn't, don't worry... in some company, I don't admit I'm that big a nerd either...

You want to shoot for 50 minutes of presentation, and then leave 10 minutes for questioning. I saw one student only take 35 minutes for presenting. That's a problem. That simultaneously makes it look like you didn't do very much, and leaves you open for 25 minutes of interrogation.

Figure: No check plus for you.
At the end of the presentation, make sure to give acknowledgments. I saw one student cry during acknowledgments, just from overwhelming emotion. I wouldn't recommend that.

When you take questions, your goal is to a) understand the question, which sometimes is no small feat, then b) come up with a satisfactory answer, preferably a "yes/no" with a reason, or a "depends" with supporting examples. Then, crucially, your job is to c) quickly take the next question before your carefully crafted aura of expertise is further assaulted.

If you make it through all questions, everybody claps again. Then everyone except university professors are dismissed from the room.


Technically any university professor can vote on whether or not you passed, but usually only the committee members will stay to deliberate, and (see Preparation section) you KNOW how they will vote. But they still have to follow proper procedure, so they cloister themselves in the room while everyone waits outside.

You and your friends stand outside the room, discussing amongst yourselves. We hypothesize that the professors actually discuss the weather and their kids for ten minutes, just to make a good show of it. Whatever they actually do, in a short amount of time they peek out the door, and you have to go back inside. They shake your hand, congratulate you, and tell you that you passed.

Then, triumphantly, you return to your friends - Doctor at last!

Post-Defense Reception

There is always a reception with snacky items afterwards. Hey, any excuse to eat, right? Normally it falls on the girlfriend or wife to take care of the reception arrangements, so you can focus on your presentation. I've actually done two receptions (including today), for friends that don't have significant others or family close by. Hey, I did it for my TA class, and all the time for my RA duties, so I'm an expert!

The reception usually also includes drinks - but different students have different styles. When a Mormon labmate graduated, we had sparkling cider. Another student (now on Wall Street) just skipped right to the other extreme and brought vodka! Champagne is most common, and that's what I did today. We polished off three 750mL champagnes at 11am. :) And one and a half orange juice cartons. Mimosas, of course...

Post-Post Defense

-The post party (if any) also depends on your own personal style. Sometimes there is no post party later that night. Sometimes, as in the case of the student who took seven years to graduate, the post party lasts well into the wee hours of the next morning. :) Sometimes the party waits until the weekend.

But whatever your own style, however you prepare, however you handle the questioning, however you celebrate, here's the thing - YOU ARE DONE!

I promise, it does happen. People do graduate. I've seen it, ten times now. May it be me some day, too. I raise my champagne glass - To a successful future defense for all of you, dear readers!

Is this how defenses go in your experience? How does it work in your department and school?

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