XKCD Comics: https://xkcd.com/1403/
It's the middle of summer, but your life's not a beach. You've spent years toiling away at the bench/computer/rig/field site, and months writing, re-writing, and re-re-writing your thesis document, only to find yourself consumed by the impending gladiatorial battle that is your oral examination. You may be wondering where to start - how exactly does one prepare to be examined? Lists of the "top 50 thesis defense questions" are abundant online and many are quite useful. Instead, I thought it might be useful to provide some basic strategies you might use to review your work though the lens of an examiner to help you predict where the questions particular to your work may arise, understand what motivates these types of questions, and devise answers that will show you've thought deeply about the work. I hope you'll find this helpful!
1. Take a 30,000 foot view of your work: It’s very easy to get lost in the details of your project, particularly after spending weeks agonizing over text and figures. However, your examiners want to know that you have an understanding of how your work fits with the broader body of literature in your field, and an appreciation for any real world applications of the work. Carve out some time to think broadly about what motivated your research question in the first place (recalling that this may be several steps away from the data you've actually collected). What do we know about the world now that we didn’t before you started? In many cases, it is a good idea to understand a bit about your examiners, and consider how your research findings might inform or relate to their fields of study.
“How should theory X be reconsidered given what you’ve shown here?”
“How would you suggest a clinician incorporate what you’ve learned into practice?”
2. Prepare to defend your assertions and assumptions: In preparing your thesis, you undoubtedly made a number of assertions and/or assumptions about how the world works (many of which may have been accompanied by references to previous work). These statements are frequently simplifications of complex processes or behaviours, and your examiners will often wish to ensure that you understand and appreciate that reality is far more complex. It is thus worth reviewing each of the claims that you've made in motivating and interpreting your work, paying particular attention to those that include or imply absolute terms (e.g., “always”, “never”) and those that may extend beyond what your data have actually shown (e.g., inferring causality).
“Is brain area A always involved in behaviour X? In what cases are the two dissociable?”
“Do the data shown here provide any direct link to the mechanism you suggest?”
3. Understand your statistical analyses: Understanding the tools you've used and the decisions you've made in analyzing your data sounds simple, but is often overlooked in defense preparation. Your examiners want to know that you understand what your statistical analyses do or do not say about your research question. Accordingly, you should take the time to understand your approach to data analysis. Consider why you chose the approaches you did (e.g., frequentist vs. Bayesian; parametric vs. non-parametric) and what the results of those tests tell you in plain language (e.g., what do p-values, R2 values, or η2 values mean about the underlying population?) Consider how outlying data points may have affected the measures you've reported, and whether the steps you've taken to address these issues protect against these effects. Consider how potential alternative approaches to analyzing the same data may have influenced the conclusions that might be drawn.
“What assumptions does statistical test X make? Were they satisfied by your data?”
“Did you perform a power analysis? How does that affect your interpretation?”
4. Know your foundational works: In many (most?) cases, your thesis was designed to build upon existing work in the field, and may follow directly from one or more core works. Examples include designing a project to test a specific theoretical framework in your field, or applying an existing experimental design to a new question. Examiners often want to evaluate how well you understand the work on which your project relies, so be sure to review these papers carefully to understand their strengths, limitations, assumptions, and core messages. These foundational works are typically easy to spot in your own work - if you’ve made multiple references to the same paper as motivation for your experimental hypothesis and/or design, you should know that work in great detail.
“Can you describe how Smith and colleagues conceptualized X?”
“How did your approach differ from that of Smith and colleagues?”
5. Prepare to show your work: Your examiners want to know that you have a clear understanding of the sometimes complex concepts that underlie your work. In many cases, it may be easier to demonstrate this visually than orally (indeed, examiners often know this and may ask you explicitly to illustrate concepts during your defense). Review your work and determine whether there are theoretical frameworks, methodological details, data models, etc. that might benefit from visual aid and either create a supplementary image that can be shared (i.e., supplementary slides hidden within your presentation deck) or practice illustrating the concepts as clearly as possible in case a relevant question should arise.
“Can you draw the model/circuit/cell on the white board?”
“Show me what the data would look like according to the alternative hypothesis?”