It can be pretty difficult knowing how to prepare for your PhD viva. Having successfully defended my own STEM PhD remotely in the last year, I want to help you to prepare! What follows are some common PhD viva questions which your examiners may ask you. Plus some additional advice based off my own PhD viva experience.
For an intro to the PhD viva including the typical structure and potential outcomes please see my introductory post:
How Much Do You Need to Prepare For A PhD Viva?
There is no hard and fast rule for how much you need to prepare. And unlike a written exam, there are of course no past-papers to practice on!
It may help ease your mind to think about what the purpose of a PhD viva is. Namely the purpose of the PhD viva (or defence) is to check that:
- You did the work;
- You understand the work;
- The research is up to the standard for a PhD.
For more detail see my separate post here including Imperial’s PhD viva mark scheme.
In hindsight I probably didn’t spend as much time preparing for my viva as is normal. Though I did unexpectedly move house less than a week before!
Besides reading through my thesis once in the few days leading up to it, I didn’t spend much time thinking up answers to questions or “revising” certain topics which could come up. The viva went fine, but it wouldn’t have done me any harm to have been a little better prepared.
It certainly helped that I’d managed to schedule a viva which took place less than six weeks after I submitted the thesis so it was all very fresh in my mind. If you submitted your thesis months before your viva I’d suggest spending slightly more time refreshing your memory in preparation for questions you may get asked.
In summary, I think it’s useful for all PhD students to get an idea of some potential lines of questioning for their oral exam!
Update: Keen to get prepared for your viva? I’ve put together a set of viva preparation worksheets which are available in the resource library. Click the image below for free access!
Common PhD Viva Questions
Listed below are common PhD viva questions which I’ve roughly grouped together. We’ll start with some higher-level questions about your PhD which should be quite easy and friendly, then progress through to some more technical (and potentially unfriendly!) questions.
It is worth noting that many examiners will ask for a short presentation at the start of the viva and this could eliminate some potential questions. In this list I’ve left in the main questions I’d expect for this presentation to address, such as what future work you’d recommend.
Very few of the questions are ones you’re guaranteed to get asked, but I can assure you that you’ll get asked at least some of them!
General PhD Viva Questions – usually friendly!
These ones are simply inquisitive and you don’t really have to worry about getting caught out. The examiners are simply interested in the work and want an insight from someone who has spent the last few years working on it.
- What is the most important finding from your PhD work?
- What was the motivation behind this research?
- Who is your research relevant to?
- Which aspects of your work are you publishing? Follow on: and where?
- What future work would you recommend?
- What are the limitations of your research?
- Which aspect of your work surprised you the most?
- What are the potential applications of your PhD research?
Method-Specific Questions – mostly friendly!
These questions dive a little deeper but even so shouldn’t be too much of a cause for concern. They come down to your own judgement and as long as you justify your decicisions you’ll be fine in answering them.
- Why did you do [things] a certain way?
- What were the alternatives to [this certain method]?
- Why did you test [that specific number] of samples?
- What effect did you think changing [something in your method] would have?
- What do you think you could have gained by using [another approach]?
- Why did you not use [another technique]?
- How did you deal with the ethical implications of your work?
Results & Analysis-Specific Questions – mostly friendly!
In a similar manner to the previous section about your methodology, you’ll often get some questions targeting your analysis and presentation of results.
- What is this graphical figure illustrating?
- Why was [this analytical technique] appropriate? Follow on: why did you use [this other technique]?
- Which of your results do you find the most interesting?
- How do you know that your findings are correct?
Literature Questions – may be less friendly!
This is where things may get tough if your examiners want to try and test your limits. Even so, they’ll still likely cut you some slack. If you have 100+ references it’s very possible that under the nerves of your exam you can’t remember specifics for each and every reference. Just don’t make things up. They’d rather you were honest than trying to deceive them.
- Please explain the key findings of reference number [X]
- Which papers would you say had the biggest impact on your work?
- What do you think are the biggest differences between [these two previous studies]?
- What have been the biggest advancements in the field over the last 10 years?
- Why did you not reference [this other study]?
- How does your work compliment the existing literature?
- What do you think the next big advancements will be in the field?
Highly Technical Questions – potentially very unfriendly!
These are the ones I was a bit scared of getting, but it is a PhD viva after all. Of course it should be expected that you have a solid understanding of the principles that underpin your project. Even so it can be unnerving thinking of how large the range of potential questions like this can be!
Unlike at a conference or in other settings where you may be able to brush over things you’re not 100% comfortable with, there is no hiding when your examiners need to test your knowledge. Particularly when they have hours of time at their disposal to do so!
- Explain how [a technique] works. This could be anything from sample preparation, equipment and analysis through to statistics. I’ve known people to get asked to explain things like a statistical t-test from first principles, with follow-on questions being asked with every answer to drill deeper.
- Explain [some fundamental concept, phenomenon or principle]. Just like the last question but applied to basic-sciences. I’ve known students to get asked questions such as: explain energy (to a mechanical engineer) and explain toughness (to a materials scientist). I’m sure we can all explain these concepts to a certain level but my concern was whether or not I could explain them at a deep enough level to satisfy the examiner.
With both of these types of questions there ultimately comes a point where you (or the internal examiner) can push back and say that answering that question was not the focus of your PhD!
What Questions I Was Asked at My Own PhD Viva
I was really surprised at my own viva how few questions I actually got in general.
The viva lasted a whopping five hours (excluding a quick break) and yet almost all of the time was spent discussing improvements to my viva to help with publishing papers.
Even so, I could have done with putting a bit more time into preparing for potential questions: which was my motivation to help you by putting together this post!
The few questions I had included:
- If you were to do the project again would you do anything differently?
- Clarification of what I meant by certain sentences in my thesis.
You may be wondering if I avoided getting asked deeper questions by the examiners because I already had a relationship with them so they were satisfied with my knowledge and capabilities. But I didn’t really know the examiners! I’d met my external examiner at a conference and he had seen me present but I’d never actually met my internal examiner before.
Instead, what I think did go a long way to helping was having already had something published in a respected journal.
Nevertheless, in a way I actually walked away a little unsatisfied by the lack of questioning at my PhD viva.
It was great to get so much feedback on my thesis which has already helped to get two more papers published since the viva, but I felt like it would have been nice to feel a bit more taxed and known that I could hold my own in the exam if it came down to it.
Now looking back on the viva 10 months later, I’m just happy to have the PhD done!
My Tips for Answering Common PhD Viva Questions
- Keep calm and take your time before answering. There is no rush to answer questions. Having a sip of a drink may help provide a pause for thinking up an answer.
- Tell the truth. If you don’t know something, just say so! It’s likely the examiners will quickly be able to tell that you don’t know what you’re talking about. Plus, there is the risk that they’ll ask deeper follow-on questions which could unravel any lies.
- Try to enjoy the experience. Think of it as a discussion, rather than a police investigation. Your examiners are interested in the work and want to hear more about it!
If you’d like personalised help with preparing for your PhD viva I am now starting to offer a small number of one-to-one sessions. For more details please click here.
I hope these common PhD viva questions can help you to prepare for your own viva.
If there are other aspects of the examination you want covered, just let me know.
I have many more upcoming PhD (and beyond!) posts. If you want to get notified about them you can subscribe here:
What would happen when you say something that you didn’t write in your dissertation?
Hi Scott, I think the specifics matter here since there are different interpretations of your question. For instance, it is possible to explain something in the viva, such as the motivation or methods, with details which you may have not included in your dissertation. In this scenario you may be asked to add these details when making revisions to your dissertation, no harm done. On the other hand, if you’ve said something in the viva which is contrary to what was written in your dissertation that’ll raise very different questions and concerns as to why what you’re saying and what you wrote do not align. It is much better to be in the former situation than the latter. Hope that helps. Best wishes, Jeff