Defending Your PhD Dissertation
So, you’ve worked extremely hard the last couple of years, perhaps published some journal articles here and there, or presented at some (virtual) conferences. Now you have one final hurdle to pass before you get the coveted Dr. before your name: the PhD defense. For most of us, the PhD defense can be one of the scariest parts of the whole PhD journey, and for good reason too — we have to present our research findings in front of an audience and our dissertation committee and then defend our results during the questioning portion. However, the defense is also the most rewarding part of the PhD journey — the time when we can proudly show our hard work to advisors, colleagues, friends, and family. So, you probably aim to make the defense presentation the best presentation you’ve made to this point.
Recently, I successfully defended my PhD dissertation and received many compliments regarding my presentation. Whether it was people from my department in the same field, or friends and family that didn’t know a single thing about my field, they all found my presentation extremely easy to understand and follow. Given how recently I just finished my defense, the stress of preparing for that presentation is still fresh in my mind. Therefore, I wanted to share some of my learnings on creating a defense presentation that showcases your work, but is easily understandable by everyone in the hope of making your preparation easier.
For some background, I received my PhD in Structural Engineering from Stanford University. My research focuses on developing computational models that can simulate the recovery and reconstruction process that regions have to go through after major disasters like earthquakes. PhD defenses may differ for different departments and universities, but my defense consisted of a public and private session. The public session was a 50-minute talk on my research — I talked about 4 of the major projects I completed as PhD student. The public portion of my defense was, as the name indicates, open to the public, and so, my friends and family were invited. The private session involves questions posed to me alone by only my committee members. The whole defense lasted for around 2.5 hours. This article will focus on the presentation for the public session of the defense. Additionally, given my discipline, this article is geared towards STEM students. However, I hope some of the learnings can be transferable to other disciplines and can be used to help prepare for other big presentations.
Before I get into my actual tips and tricks, I would like to preface this article by saying that a great presentation takes a lot of time to prepare. There is no way around it. Granted, you can always make the presentation a couple days before your defense, copy and paste several figures you’ve made in the past, add in a couple of bullet points to demonstrate your points, practice a couple times, and then head into your defense. But if you’re here reading this article, I assume you want something more. You don’t want your final presentation to be a boring presentation where the slides are filled with text and unreadable figures. My defense presentation took a total of around 65 hours to create and rehearse (yes, I kept track in my calendar), and I started making the presentation around 3 weeks before my defense. How much time you put into preparing for your presentation will ultimately depend on you. Still, if you want this to be the best presentation of your life, you’ll have to put some work into it.
The three main parts to think about when creating your presentation is: content, design, and delivery. Throughout this article, I will also be showing actual examples based on my experience preparing for and creating my presentation.
Part 1: Content
Unsurprisingly, the content is the “bread and butter” of your presentation. As PhD students and researchers, we are experts on the subject matter, so given a chance, it is very easy for us to talk on and on about our topics. However, in a presentation that lasts for only 50 minutes, this can be the problem itself as we might be tempted to go into the details, and we can lose the attention of the audience, even those from our own field.
1. Carefully choose results to present
With the limited time we have to present all that we’ve done throughout our PhD studies, it is likely to be impossible for us to cram every single result we obtained into our presentation. One of the simplest and most effective ways to start structuring the presentation is to choose three main topics or projects that you’ve done. This might correspond to the three main chapters of your dissertation. If your dissertation has more than three main chapters, then you can either: a) combine some of those chapters into a broader topic or b) choose 3 of the most interesting chapters to present. In my presentation, I went with option (a).
Once you’ve selected your 3 main topics or sections of your presentation, the next step is to determine which results are most important for that topic. This is an iterative process, similar to the process of writing a journal article — it takes multiple drafts or iterations. The content you put into your final presentation version will change as you keep on working on it. In fact, I didn’t finalize my presentation until the day before my defense.
Some things I thought about when choosing results to focus on:
- Is there a single number that can be used to represent the results? For example, I developed a model that resulted in a X% reduction of error compared to existing models. Using this kind of number is an easy way to demonstrate concrete results and is easily understandable to everyone.
- If there were multiple experiments or versions of case studies, choose the experiment/case study that resulted in the most significant impact. The audience understands that we put a lot of effort into the research, so you don’t need to present every single experiment iteration you performed.
- If you had many similar results, choose one to present and then make clear in your presentation that all the other applications had similar results. For example, I applied my model to 6 different regions in one of my studies. In my presentation, I noted that although I had applied the model to 6 regions, I presented results for only 1 region.
The figure below shows how I presented results for only a single region and demonstrated the results that had % reductions:
2. The simpler, the better
As I mentioned earlier, as researchers and scientists, we are very tempted to show how well we know our subject by going through all the details. As a result, we might want to show all the things we did to demonstrate how much work we put into our research. Examples of this are presenting every single equation in our slides, putting in every single assumption, or including every tiny detail of our methods. Avoiding this temptation might be the hardest thing for researchers to do, but putting in too much detail will not help anyone — you or the audience.
As the primary researcher of the work, you, and only you, are the one that knows the topic inside out. Though your dissertation committee might be knowledgeable, they don’t know everything about your topic as you do. And be honest, do you understand and know everything about what your colleagues in your research group are doing? Probably not. The audience doesn’t need to know all the details of your research to understand it. So, you don’t need to put the details into the presentation.
Below is an example of one of my optimization problems in my dissertation. As you can see, it involves many variables and constraints, and it would take me a significant amount of time to explain each one. In addition, though the constraints are important to the problem, they are not critical for the audience to understand.
I decided that the most critical aspect that the audience should understand is the main objective and a general idea of the constraints. Therefore, I ended up simplifying the constraints into straightforward language. Here is what I ended up putting into my presentation slide:
Of course, how much you simplify your equations might depend on your discipline. I mentioned previously that the equations are not the main contributions of my research. However, if your equations are your contributions, then, by all means, you should put them into your presentation. However, only put those that are absolutely needed. If you are not going to explain an equation during your presentation, delete it.
3. Prepare backup slides
Don’t worry about not including enough details in your presentation. Your main presentation should be focused on getting the overall story across. Instead, you can put details or content that don’t end up in the main presentation into backup slides. These slides won’t be shown during your main presentation, but they will be extremely useful if someone asks about a particular detail; you can then whip out a slide specifically about that detail. It also makes you look super prepared! And that will further impress your audience!
My main presentation had 38 slides, and I had an additional 20 slides as a backup. And yes, I did end up showing some of the additional slides during the private session with my committee members. They proved to be very useful in clarifying some concepts.
As a brief example, there was one slide in my formal presentation in which I explained the difference in parameters between the model I was proposing (Queuing Model) vs currently existing models (Time-based Model). The figure below shows the slide I’m talking about:
I could have gone into detail about each of those parameters and how I obtained them. How did I obtain the lognormal parameters for the delay time or the construction time? However, I did not explain how I obtained those parameters during my presentation. I saved those details for a backup slide to use when I talked to my committee alone. Below is the backup slide I prepared for that:
Part 2: Design
How many of you have sat through a research talk where the slide deck looked like it was created 20 years ago or was just not appealing? Probably most of us. I always strive to make my presentations aesthetically pleasing because why can’t a research talk be both informative and pleasant to look at? And no, you don’t need any design skills or experience to create a presentation that is pleasing to look at! Here are some tips I have:
1. Use a simple and clean template
Choose a presentation template that is simple and clean. Some universities may provide you with a standardized template, and it might be the case that you have to use the provided template. However, if you are given the option, I usually stay away from standardized templates because of two reasons: 1) the template is probably old, and therefore, the design looks outdated or 2) everyone uses it, and therefore, it doesn’t look fresh.
With a presentation such as your defense, you want the audience to be as excited about it as you are! And if that means choosing a different template no one has ever seen before, then so be it!
I ended up choosing and modifying the “Basic Color” template from Keynote (sorry, Windows users), shown below. It is clean and simple, it has a solid color for the background, there are not too many random accents here and there, and the fonts are easily readable.
2. Choose a consistent color scheme
Do not vary your color scheme. The color scheme is a set of colors you should use consistently throughout your presentation. For a presentation to be aesthetically pleasing, the color scheme should apply across every single element in your presentation, whether it be your fonts, backgrounds, figures, or illustrations.
I previously mentioned that I modified the “Basic Color” template from Keynote. Specifically, I changed the color scheme of the template. The original template I chose from Keynote used blue as its primary color, but Stanford University’s color is red. Therefore, to add a little Stanford spirit back into my presentation, I changed the color scheme to a combination of red and blue. I thought that Coolors is an excellent resource for choosing color schemes!
Using my chosen color scheme, I applied it throughout my presentation, as seen below:
Using a specific color scheme consistently throughout your presentation makes your presentation flow. It makes it easier for your audience to understand and remember your material better. For example, I talked about the different income levels of a household: very low, low, moderate, and high income. For each of the income levels, I selected a different shade of blue. And throughout the rest of the presentation, I used those colors every time I mentioned income levels. See below for an example:
3. (Re)create figures for your presentation
This might be the last thing you want to hear, but you should create figures specifically for your presentation. I know this seems like a lot of effort, but I found that most of the figures I created for my journal articles and dissertation didn’t fit into my presentation. This was either because the font was too small, the colors did not match the color scheme of my presentation (see points above), the dimensions do not fit, or it was too difficult to understand the plot (more on this later). It might also be that you realized there is a better way to represent your results.
Here, I’ll give three examples of how I ended up creating or recreating my figures.
a. Recreating figures to better represent results
When creating my presentation, I found that specific figures in my paper were just not optimal for a presentation. To make the content simpler, or for better flow in my presentation, I had to recreate it from scratch.
An example of this would be the figure below, which is found in one of my published papers:
The above figure was a figure I created during my early years of PhD, and I’ve definitely learned a lot since then. In particular, I knew there was a better way to visualize it for my presentation. Below is the recreated version for my presentation. Notice that I also changed the colors to match the color scheme of my presentation (more on this on the next point).
b. Recreating figures to be consistent with color schemes
Early in my presentation, I introduced the concept of building damage levels, which are discrete categories that buildings are classified into after earthquakes based on how much damage is present. There are three categories: minor, moderate, and major damage buildings. Early in my presentation, I used three distinct shades of red to indicate each damage level. The image below demonstrates this:
However, a key figure in my journal paper/dissertation did not use the same color schemes. Therefore, to keep the color scheme consistent, I had to recreate a figure to align with the same color choices as the one in my presentation. This may seem like an unimportant detail, but it will help the audience’s comprehension–it is easier to follow information that is consistently presented and follows a “pattern.”
c. Recreating figures to emphasize a point
Because there is only a limited time for your presentation, you may want to emphasize a specific part of a plot. I recreated some figures to make the audience immediately focus on the most important element.
For example, in one of my figures, I wanted to emphasize that the results obtained with my proposed algorithm (Greedy Order) are better than those obtained from other algorithms. As a result, I made the line representing the results with the Greedy Order thicker than the others:
One final note of figures: remember to make your legend consistent throughout! This can refer to the order in which the legend labels are presented or the labels themselves. Does the audience know what the labels mean? Have you mentioned it previously, or do you have to explain it to them?
4. Integrate “breadcrumbs,” or signposts, to help the audience navigate your presentation
Including additional design elements to help the audience follow along during the presentation is beneficial. Such elements allow your audience to know what to expect and to see where you are in your presentation, which will keep them more engaged:
- Page numbers: This is mandatory and should be included in every slide of your presentation. It makes it easier for the audience or committee members to refer back during the Q&A portion.
- Navigation bar: This is something I find very useful, especially when listening to other people’s research talks. A navigation bar is a visual indicator of where you are currently in your presentation. There are several ways you can do it, but I usually create a horizontal bar on the bottom of my slides with the main sections of my presentation. During a specific section of my presentation, I bolded the text of the section I was currently on and faded out the other sections. See below for my navigation bars:
- Visual outline: This is another method to let the audience know where you are in your presentation. It is a good method to show the audience when introducing the arc of your presentation in the beginning. It is also a good method to indicate to the audience that you’re moving on to the next topic. Finally, it is also a great way to wrap things up. See the slide I created for this below:
Part 3: Delivery
Last but not least, how you present your presentation can make or break your presentation!
1. Use animations!
I cannot emphasize enough the importance of using animations in your presentation. If you take only one thing out of this article, it’s that you should definitely make use of animations! I don’t often see people leverage animations enough, and I get it; it takes a lot of time to create them. But let me tell you, it is definitely worth it. Animations are the best way to explain complicated processes without losing the audience. With animations, you can build up complicated slides and walk the audience through it. Animations also allow some variation in your presentation that will hold the audience’s attention. Talking about the same slide for over 5 minutes without any change will not help the audience’s focus.
You might have noticed that some sample slides I’ve shown you thus far are very packed. And that is true. I do tend to pack a lot of information into a single slide. However, it is important to note that I do not immediately show the complete slide to the audience. Instead, I use animations to guide the audience and continuously build the slides until it has all the necessary information.
Here is an example of one of my complicated slide:
If I had immediately presented this whole slide to the audience, the audience might likely have felt overwhelmed by so much information. Their attention would have wandered even if I had a laser pointer to help me explain this slide.
Instead, I took my time with this slide. I made use of animations to build the slide slowly. I explained that households are classified into several income groups: very low, low, moderate and high income. I explained that many different funding sources are available to reconstruct a house. I then explained in detail what each of the different sources are. In total, I probably spent over 5 minutes on this slide alone.
Here is the slide again with all the animations in place:
Doesn’t this animated slide just look much better and more understandable?
In addition to building up the slide, as shown by the example above, animations can also be applied to the figures in the slides. There are a lot of complicated figures in my research. If I were to show such a figure immediately to the audience, there is a good chance that they will not immediately grasp all of it. To prevent this, I use animations to build up my figures. First, I explain the axes: what do the x and y axis represent? I think that this is one of the most underrated aspects of a good presentation. Because we are the ones that made the figures, we tend to assume that the audience will immediately understand our figures. The truth is, they probably will not. So take some time to explain what your axes mean! Only then will I start to explain the actual results of the figures.
This is where recreating your figures comes in! Because of my figure’s complexity, I recreated my figure to first show only the axes. Then, I recreated the figure to include parts of my results. As a result, I can animate it like the examples below:
Last, you can use animations to emphasize specific points or transitions. One small animation I really like to use is fading out certain elements of my slide to show that we are now moving on to a different topic. This might seem like a small aspect, but it is pleasing to look at. Here is an example:
2. Always start with your motivation or the “gap” or problem your work addressed
Whether this is the start of your entire presentation or the beginning of a new section or project you’re about to explain, always start with your motivation, and don’t be afraid to spend some time to make sure that your audience understands why your research is important. If the audience understands this, they are more likely to be invested in your presentation.
A friend gave me a really good suggestion on how to explain my motivation. First, explain the context, the current condition of the topic in the world, or the state of existing literature. Then, phrase the motivation as a question. When framed as a question, it’s easier for the audience to understand why you’re doing the research.
For example, one of my research projects focused on determining which damaged hospitals should be rebuilt first after an earthquake. The problem is, decision-makers don’t have unlimited resources (money, labor, materials, etc.) to simultaneously rebuild all hospitals if many hospitals are damaged. Therefore, they have to prioritize certain hospitals. The question I posed for the audience was: Given limited resources available, which facilities should be rebuilt first?
3. Zooming out to transition
With a heavy topic like a dissertation defense, it’s extremely easy to get sucked into the details of each study or project. That was one of my errors early on when preparing for my defense. I was too engrossed in my work to notice that I was not connecting the dots between my studies. I only realized this after rehearsing in front of some of my colleagues.
I like to think of my presentation in the following format:
Start with a big picture overview of your research in the introduction. Then, go deep into your 1st project or study. But, when moving onto your next study, make sure to zoom out again and remind the audience of how your studies relate to one another. This is where you can use the visual outline I explained previously when creating “breadcrumbs”!
For example, this was my transition words that I used to move to the next section of my presentation:
“Up to this point, we’ve talked about reconstruction crews. But as I mentioned in the beginning, there are many different types of reconstruction resources. So now the question is, what if we consider financing? How does financing further affect recovery?
Note that I used time signifiers in my transition to show how my studies related to the overview of my research. This zooming in and out should be done with each transition to a new topic/focus and will further aid your audience in keeping track of where you are in your presentation.
4. Practice makes perfect
Rehearse your presentation! I know this may seem obvious, but practicing your presentation is crucial, especially because there are animations in your slides. The ordering in which you deliver your main points is directly tied to your animations; therefore, you can’t really go off script as much as you can if your slides did not have animations.
By running through my presentation multiple times, I realized that certain parts did not flow smoothly or that other things were not even necessary. Most of the helpful edits to my final presentation resulted from my repeated practicing. And of course, don’t only practice by yourself, but carve out some time to actually rehearse your presentation in front of your advisor and/or research group. I definitely thought that the most useful comments and suggestions I received came from my colleagues! They gave me a completely different perspective and made me realize certain areas were not clear at all, even though I could’ve sworn the information was crystal clear.
Last but not least, here are some final tips before your big day:
- If possible, rehearse your presentation at least once in the exact room you’re going to present. My defense presentation was a hybrid format; therefore, some people joined through Zoom. In the rehearsal, I replicated the exact conditions of “D-day” as much as possible. I set up the computer and camera, set up the Zoom, recorded the meeting, and had someone enter the Zoom meeting room to make sure they could see my screen and hear my voice. Setting it all up took a lot of time, but I am glad I took the time to go over the technology before the actual defense.
- If your presentation is hybrid or online, choose someone to be your co-host. Your co-host can deal with the participants (there will always be someone who forgets to mute themself) and monitor the chat. That way, you can focus on your presentation.
- What is the ratio of the screen in the room you’re presenting? Will it be an older projector, or will it be a flat-screen TV? An older projector will most likely use a 3x4 ratio, whereas a TV will most likely use a 9x16 ratio. This might affect the way your presentation slides are presented, so check to make sure!
- Use a wireless pointer to advance your slides without having to be in front of your laptop. Test it out at least half an hour before your presentation to make sure that the buttons actually advance your slides. And don’t forget to check the battery the night before!
And there you have it! These are some of the best practices I learned while preparing for my defense presentation, divided into three main categories: content, design, and delivery. I honestly had a lot of fun preparing my presentation slides, and I hope this article will help inspire you and help you enjoy the preparation process too! Though this article was geared particularly towards a STEM defense presentation, I believe you can apply some of these best practices to other disciplines and big presentations besides the defense.
Last but not least, remember that the defense presentation is YOUR day. So, prepare well for your presentation, but remember to take some time off to relax before the day. When the time comes for your defense, don’t forget to enjoy the moment and be proud of all you’ve accomplished leading up to that point! Good luck!