Preparing for your thesis defense

The thesis defense. The very name suggests a confrontational event. And yet, in my experience, it doesn’t have to be. A well-prepared student should have nothing to fear from their defense. Indeed, it’s often more like a conversation among peers than like an examination. However, if you’re not well prepared, it can turn into a highly unpleasant grilling.

You will of course wonder how you can prepare for an event that seems, to many students, unpredictable. And yet, it’s not.

Know your thesis.

The examiners are going to ask you questions about your thesis. This sounds obvious, and yet it often seems as if students show up unprepared for this eventuality. You should be the foremost expert in the room on the material in your thesis, with the possible exception of your supervisor, who ought to be on your side. (And if he or she is not, then you have problems that predate your defense. But that might be a topic for a future blog post.) A fairly common question, usually prompted by genuine curiosity about a passage an examiner didn’t quite understand, runs along the lines of “You wrote such and such on page x. What did you mean by that?” If you can’t answer this question, or if you give an obviously incorrect answer, you are in trouble. This should be an easy question for you to field since you wrote your thesis and should know exactly what every word and phrase in it means. Examiners think of such a question as a gimme, and often ask questions of this sort early in the defense to relax the candidate. Again, you’re supposed to be able to answer these easily.

So why can’t some people answer such questions? Putting aside brain freeze, there are only two answers I can think of:

  1. You didn’t actually write parts of your thesis. In today’s world where a thesis is often a collection of papers, it’s not unusual for a student’s thesis to contain text that they didn’t actually write, which is OK (if your university allows a thesis that is compiled in this way) provided you acknowledge it properly (which students sometimes fail to do). Of course, you may simply have plagiarized some of your text from somewhere. If it’s the latter, you’re in serious trouble now, because the examiners can smell a rat and will likely find you out. You should have read my posts about plagiarism (here and here) before you started writing your thesis, or at least before you submitted.
  2. You wrote it, but you borrowed some wording from somewhere (a paper, your supervisor) that you didn’t fully understand.

Whether parts of your thesis were written collaboratively or you used a clever turn of phrase you heard somewhere, there’s simply no excuse for not knowing what the words in your thesis mean. In either case, you need to make sure that you have read and understood every line in your thesis. If someone else wrote some of the text and you’re not sure what it means, ask them. If you ended up using a phrase that sounded good but that you didn’t quite understand, find out what it means. Again, questions like this often come early, so you’re getting off on the wrong foot if you can’t answer them, or if you answer them in a way that shows you have no idea what parts of your thesis mean.

A closely related issue is understanding the techniques used in your thesis. This is often a problem in collaborative work. It’s fine if other students or collaborators carried out an experiment that is discussed in your thesis. What is not fine is not understanding the experiment. You really ought to be able to explain every experiment described in your thesis, as well as the results of those experiments.

Yet another related point is that you ought to be able to explain results or experiments from other papers that you mention in your thesis. If you say “property X was measured by method Γ”, then you ought to understand how Γ works.

Be broadly aware of your field.

I always tell my students that they need to read papers in their general area of research. This goes double for students preparing for a defense. A lot of the questions at your defense will ask you to think about how your work connects with other work, or about how your work fits in to the bigger picture in your field. You can’t do that unless you have read papers in your general area outside of the specific, narrow topic of your thesis. You should be taking opportunities to broaden your knowledge base throughout your time as a graduate student by reading, but also by attending seminars and conferences. Even if you have been doing that, the gap between thesis submission and the day of the defense is definitely a time you should use to do some extra reading and to think about how your work fits into a bigger picture.

Because this is actually where most of the time in your thesis examination is likely to be spent, I’m going to emphasize this again: Be prepared for big picture questions. Think about what kinds of big picture questions the examiners might ask. Read materials that will help solidify your own understanding of the big picture in which your research is embedded.

Know your examiners.

The identities of a student’s examiners aren’t a secret, and yet some students take no account of their examination committee when preparing for their defense. If one or more of your examiners works in your field (typically the case for your external examiner, for example), you need to read a few of their papers. Perhaps you have already, and you may even have cited these papers in your thesis. For the other examiners, you should at least find out what they do, say from their web pages, and think a bit about questions they might ask given the perspective they bring to your defense. If one of your examiners is a protein structure person, even if it’s only tangentially related to your thesis, that person may ask structural questions about some of the molecules you mention. If you can ace those questions, you get lots of bonus credit. These may not be critical pass/fail questions, but knowing a little bit about an examiner’s interests can help the whole event go more smoothly.

Check out another student’s thesis defense.

At the University of Lethbridge, thesis defenses are open events, meaning that anyone can sit in on a defense. If that’s the case where you are, make sure to sit in on one or two thesis defenses before your big day. This will give you an idea of what happens at these things, and might help you get past the fear many students experience regarding their defense. It’s really not that bad.

Get some sleep!

You’ve had the pedal to the metal for several months leading up to your thesis submission. You’ve been burning the midnight oil, in fact, burning the candle at both ends. You’ve been busy as a beaver, working like a dog, going at it hammer and tongs. You’re tired.

Now that you have submitted, take some time for you. Make sure you get your sleep, eat well, and exercise. A well rested candidate is one who is likely to be able to think on his or her feet. A tired candidate is likely to flub the easy questions.

Some closing thoughts

When you were an undergraduate, you didn’t know what questions the professor was going to put on the exam. You did not let the uncertainty paralyze you. You studied, reasoning that if you had a good understanding of the material, you would do OK. Maybe you used what you knew about the professor to guess where the major emphasis might be. A thesis defense is not all that different. The material consists of your thesis and of closely related areas of science. Knowing who the examiners are, you can guess what their general areas of questioning might be. Now all you have to do is to study the material. If you made it all the way to thesis submission, you’ll be fine.

In a future blog post, I will talk about the thesis defense itself. Stay tuned.

3 thoughts on “Preparing for your thesis defense

  1. dammy

    Thanks for this information. I actually find this thoughtful and will help me in my upcoming defense. But a question for you Marc! What is you are not able to answer a question that was asked by the examiner, maybe because it a little outside of your area, and as such don’t want to say ” I don’t know” . How can you address that question?

    Looking forward to your reply and your next blog.

    1. Marc Roussel Post author

      What a great question! I was planning to address that one in my next blog post, which will be about the actual defense, and which I plan to have out in a week or two.

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