Doctoral Dissertation Defense Presentation


Well, I’m back. After 3 months of intense thesis writing, revisions, and successfully defending (all while working a part-time job in industry), I want to share with you Part 1 of 3 of this series. Part 2 will be how to finish your thesis in a timely manner (and write a good quality thesis). Part 3 will be life after a PhD, making the transition into the workforce, and how to prepare ahead of time (i.e. apply for jobs before, during, or after writing your thesis).

First, what does it take to give a successful PhD Defense? How can you prepare, keep the stress levels low, and make sure you have the highest chance of success?

I’ll just say that everyone’s PhD Defense is unique and is unpredictable. Your talk/presentation is only as good as you want it to be. And you cannot fully prepare for all the endless possibility of questions. If you wrote a 200 page thesis, your thesis commitee can pick apart an error bar on a graph on page 133. They can ask you what you meant by a word in a random sentence in any given paragraph. Keep in mind, this is all just apart of the PhD hazing process, and in a sense is just to humble you. At the end of the day, if you wrote a good quality thesis and are CONFIDENT, you should have no problem successfully defending and leaving that room with a sense of relief. Either way, I wanted to share my experience while it is still fresh in my mind

1) Do not underestimate how long it takes to prepare your slides/talk and make sure you give multiple practice talks

When I turned in my thesis two weeks ahead of time to my committee, I thought the hard part was over. Although a very important milestone, don’t let your guard down. If you already have most your slides ready to go, then you are lucky. I ended up getting data at the last minute and my story changed. I had to make many model slides from scratch.

If you want to give a GOOD thesis talk, you need to practice multiple times. And this means that you don’t cram it all in a couple of days right before your talk. I’m not talking about giving just one practice talk. You need to give multiple group practice talks. In between, you need to practice on your own.

You certainly don’t have to memorize every word of your thesis defense talk, but you should have it well-polished. There is no limit (or requirement) on how many practice talks you should give, but give as many talks as it takes until you feel like you are ready. If you are unsure of the quality of your talk (or being “ready”), tape record yourself or watch a video of yourself to see just how good it is. You might be surprised when you play it back to yourself.

You should also time your talk. I noticed that I tend to talk faster (by about 5 minutes) when giving the actual public talk vs. when I practice on my own. The length of the talk can depend on many departmental factors. My talk was ~45-50 minutes long which also leaves time for questions.

Either way, do not procrastinate on your slides and/or talk until days before. Make sure you use the full two weeks to perfect your slides, polish your talk (and be very concise about your words), and review material you are unsure about.

2) Listen to other thesis defense talks

The best way to mentally prepare for your thesis defense talk is to listen to other thesis defense talks. I actually went and got a few talks on DVD (the good ones that I remembered). If their research is on a similar topic as your own, this would be more ideal-but take what you can get. When you watch the talk, ask yourself what makes it good or bad? Were they enthusiastic and sincere? Did they keep the energy throughout the talk? Were there some rough areas of the talk? When nerves are running high, talks may not go as expected. You can battle this nervousness by showing up well-prepared. If you are, the thesis defense talk is just a formality.

If you cannot obtain any thesis defense talks on video, make sure that you go to actual public thesis defense talks. At least go to one so that you have a good idea of how to TIE the whole story together and give your audience the big picture. Keep in mind that you are giving a talk to a general audience. This means that use of jargon and highly technical terms will only put your audience to sleep. Make sure it is clear and understandable. Simplify it the best that you can and put it in the larger context of your research field. Use cartoons or model slides (if necessary) to give your audience the general, overall picture.

3) Have your friends, labmates, and others drill you with questions

What’s the best way to prepare for unforeseen questions? Have others that are familiar with your work drill you with questions. Chances are that even though these questions may not be the actual questions you will be asked either by the public and/or your thesis committee, it prepares you to think on your feet. It also builds your confidence. And the questions that your labmates or friends ask you may just be the same question you will get asked on your defense day.

4) Re-read over your entire thesis and write out your own list of questions

You may be sick of reading your entire thesis over and over by now, but you need to keep everything fresh in your mind. I actually read over my entire thesis multiple times during my final two weeks and came up with my own list of questions that I thought my committee would ask me. In addition, I also came up with a list of questions that I had of my own (questions that I was unsure of or that I thought were a weakness of mine). If you cannot come up with a list of good questions, then you are not trying hard enough.

Even though my committee didn’t ask me my exact list of questions, the process of  coming up with my own list of questions-then finding the answers to those questions (beyond my thesis)-actually helped me gained a deeper understanding of my project. And it was a confidence booster in disguise.

5) Don’t let distractions get to you

Completing your thesis is a huge milestone. Those last two weeks until defense day can be stressful. Whether you are doing job interviews, applying to other jobs, or you want to “jump the gun” and finally start your post-PhD life, don’t give into temptation. Keep your guard up until your actual defense day. This is key to giving a good talk. You need to go in with the mindset that you will kill your presentation and give a long lasting impression to your audience. I have actually heard that some people who gave great thesis defense talks were offered a position shortly after (i.e. a postdoc).

You are going to want to do all those little tasks that you have been putting off for so long because you have spent X amount of months writing your thesis in solitude and you had no time to do them. Your list could be very long. I can tell you that one of the things on my list was to keep publishing blog articles and keep my blog running. I simply did not have enough time. Prioritize and focus on your defense talk and nothing else. If you are looking for jobs during this time period, I will be writing about this in Part 3 of this series.

6) Get plenty of sleep, keep your diet in check, and take care of yourself

This might be the most difficult thing for anyone. I struggled with this the most while writing my thesis. Skipping meals, late nights, overloading your system with caffeine just to stay awake. You have to fight it the best that you can. A month before my defense talk, I hit the gym 3x a week (for the first time in months). Everyone handles the anxiety of their defense talk differently. I am someone who thinks about it constantly. So it becomes hard to focus on other things, like taking care of yourself.

Once your thesis is turned in to your committee members, during those final two weeks- sleep and a proper diet are KEY. The day of your defense, make sure you are well-rested (don’t stay up all night stressing about it) and eat well. Don’t sell yourself short. By taking care of yourself, you ensure that you have the highest probability for giving a great thesis defense talk and showing your committee members that you are confident about your project.

7) Keep your cool and relax

When your defense day comes, you have to remember that you have put in a lot of HARD WORK to get to this point. You know your topic better than anyone. Because of this, you have no reason to be stressed out.

When your committee pushes you and asks you questions, they again will push you to your limits. You will meet a point where you won’t know the answer. Also, a question could simply be a future direction/experiment that you simply haven’t tested yet. Remember that they are simply trying to test your knowledge and humble you. You don’t have to know all the answers. Therefore, when you are answering questions, keep your cool and relax. Answer the questions the best that you can and you should have no problem passing. And in all honesty, the prelim (or qualifying exam) was much harder than the actual defense…

8) Don’t focus on the after-party until you have actually reached the after-party

Who doesn’t want to spend their final two weeks planning the celebration? Although I did have an after-party, I did not go to great efforts to plan it like a wedding party. As I said in #5, prioritize and focus on your thesis defense talk and nothing else. Plan your after-party while you are on break from your practice talk/preparing for questions/working on slides but do not make it a number one priority. Once you have passed, then you can change your focus. The feeling is indescribable (see #10).

9) Have a good structure

A good thesis talk also has a good introduction before going on to the next idea or slide. It should flow in a logical manner and be smooth. That is why #1 is important, because many people don’t spend enough time in the creation of good powerpoint slides. Your slides and talk have to MATCH up, meaning you can’t have really good slides and a mediocre talk (or vice versa) if you want it to go well.

This is why practice is important, and if you spend enough time on BOTH the talk/slides you will give a very good talk. A lot of times while I was actually practicing my talk, I had to go back and change the order/wording of slides or how I introduced certain slides (the wording) so that the flow would be better.

Be formal in how you word things (i.e. say “our data show that”… vs. “you see here that”…). To give a good introduction, it might be wise to use slides that ask a question in between. This question slide (break) in-between your next idea allows for your general audience to CATCH UP and understand your logic. Why are you doing this experiment? If you just show a bunch of your published data with no introduction (and maybe a title that gives an interpretation/punchline), you will overwhelm and bore your audience.

Many scientists forget that although they are an expert on their topic, what seems easy and understandable to them-does not apply to others outside of their field.

Before you go to your next data slides introduce the idea (based on this data I wanted to ask this question). Then tell them WHY you performed this particular experiment (which is basically in the form of a question). Once your audience understands why, go on to the next slide and give them your interpretation. In other words, don’t just jump to the interpretation. This will keep your audience’s attention and make sure that your thesis defense talk gets a lot of positive feedback and leaves a good impression on your committee members (it really does show).

10) Visualize yourself giving your defense each day and think about how good it will feel when it’s over

This one is pretty self explanatory. I will say that when it is all said and done, it feels like a huge burden has been lifted off your shoulders. It is emotional and you finally feel that all that hard work and time that you put in over the years-was all worth it in the end. Good luck to all those who are preparing for their defense talk in the future! Think about what it will be like to get up in front of a large audience and show everyone how you moved a field forward. This is YOUR moment to show everyone you are an expert in your field. The more you keep this mentality, the better your talk will be. Keep your cool and relax (#7) and everything will be fine.

If you would like to see an example video of a defense talk that illustrates the advice I’ve given, a link to my PhD defense can be found here: http://bit.ly/1sAIT7O

Best of luck to all!


Further Reading

What is a thesis defense?

Chris Riesbeck


What is a thesis defense?

A thesis defense has two parts: a thesis and a defense. The second mistake many students make is not knowing what their thesis is. The third mistake is not knowing how to defend it. (The first mistake is describe later.)


What is a thesis?

Your thesis is not your dissertation. Neither is it a one liner about what you are doing. Your thesis is "a position or proposition that a person (as a candidate for scholastic honors) advances and offers to maintain by argument." [Webster's 7th New Collegiate Dictionary]. "I looked at how people play chess" is not a thesis; " people adapt memories of old games to play new games" is. Similarly, "I wrote a program to play chess" is not a thesis; "playing chess requires a database of actual games" is. A thesis has to claim something.

There are many kinds of theses, especially in computer science, but most of them can be lumped into one of the following classes:

  1. process X is a feasible way to do task Y
  2. process X is a better way to do task Y than any previously known method
  3. task Y requires process X
  4. people use process X to do task Y
  5. process X is a terrible way to do Y
  6. people don't use process X

Feel free to substitute "process X" with "memory organization X" or what ever else might make one theory different from another. Make sure you clearly specify the class of tasks Y to which your thesis applies.

Besides being a proposition, a thesis has to have another property: it must say something new. "Understanding natural language requires context" is not a thesis (except maybe in a linguistics department); "process X is a feasible mechanism for adding context sensitivity to natural language understanders" is, as is "context is not required for visual understanding.


What is a defense?

A defense presents evidence for a thesis. What kind of evidence is apprpropriate depends on what kind of thesis is being defended.

Thesis: process X is a feasible way to do task Y

One defense for this kind of claim is an analysis of the complexity, or completeness, or whatever, of the theoretical algorithm. In computer science, the more common defense is based on empirical results from running an experiment. A good defense here means more than one example, and answers to questions such as the following. What are the capabilities and limits of your experiment? How often do the things that your experiment does come up in the real world? What's involved in extending it? If it's easy to extend, why haven't you? If your example is a piece of a larger system, how realistic are your assumptions about input and output?

Thesis: process X is a better way to do task Y than any previously known method

The same kind of defense applies here as in the previous case, but now serious comparisons with previous systems are required. Can your result do the same examples the previous results did, or can you make them do yours? Can you prove they couldn't do your examples? If you claim to be more efficient, what are you measuring?

Thesis: task Y requires process X

This is usually defended by a logical argument. It is usually very tough to do, even if the argument doesn't have to be formalized.

Thesis: people use process X to do task Y

Many students make the mistake of picking this kind of thesis to defend. It requires serious experimental evidence to defend, unless your real thesis is of the previous form, i.e., only process X is possible. Selected excerpts from protocols and surveys of your officemates are not psychological evidence, no matter how much they might have inspired your work.

Thesis: process X is a terrible way to do Y, or people don't use process X

This is a reasonable thesis if process X is a serious contender. The defense would be an analysis of the limits of process X, i.e., things it can't do, or things it does wrong, along with evidence that those things matter.


I have lots of theses in my dissertation. Which one should I pick for my defense?

Defending a real thesis is hard. If you think you have a lot of theses, you probably just have a bunch of undefended claims. One good thesis, or two so-so theses, with adequate description and defense, is more than enough to fill up a dissertation.


I have the opposite problem. I don't think I have any thesis by these standards.

Highly unlikely. If you're bright, educated, and have worked hard on a topic for more than a year, you must have learned something no one else knew before. The first mistake that students make is to think that a thesis has to be grander than the theory of relativity. A thesis should be new and interesting, but it doesn't have to change the foundations of all we believe and hold dear.

Don't try to come up with a thesis first, and then investigate it. Start by exploring some task domain. Take some initial ideas and push them hard for a year or so. Now, stop and think about what you've done and what you've learned. Among your accomplishments and experience, there will be several good candidate theses. Pick one. Test it out on your advisor and other faculty members. Test it out on other students. Is it a claim that you can describe clearly and briefly? Is it a claim that anyone cares about? Is it a claim that people don't find perfectly obvious, or if they do find it obvious, can you convince them that it could easily be false.

Once you've refined your claim into a good thesis, now you can determine what kind of defense is appropriate for it and what more you need to do. This is where the hard part comes, psychologically, because to create a defense for your thesis, you're going to have to attack it harder than anyone else. What happens if the thesis fails? Negate it and defend that! In a year or so of focused research, you should be ready for a real thesis defense.

See how easy it is, once you know how?


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