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So I have to defend my master thesis in computer science in two weeks. It's in Germany and the thesis is 30 credits. I'm wondering what could make someone fail his defense? In my thesis I mainly compare different approaches and algorithms and did experiments on them to answer some research questions. Would I fail if, for example, during the discussion a mistake in my comparison and evaluation approach is discovered which makes my results meaningless? Although I discussed my approach and everything I did with my advisor (postdoc not the prof), yet I still fear that I might have done something wrong and then everything collaps.

I still remember reading a question on this site where someone mentioned that he discovered a vital mistake in his PhD thesis after two years of the defense which made almost his entire thesis useless. Yet of course he didn't lose his PhD degree. So if something like this happens, but during the defense, what could happen?

So how would one fail his master thesis defense? Just to calm down a bit and feel safe and secure!

Edit: I passed with an excellent grade :D.

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    Your advisor should not let you defend if you are not ready. Ergo, your advisor thinks you are ready. Stop worrying and go for it! – Bob Brown Mar 15 '15 at 18:24
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    Ideally, an advisor should not let you defend if you are not ready; unfortunately, some advisors still do let not-quite-there-yet advisees defend anyway. – Mad Jack Jun 1 '16 at 17:27
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Would I fail if, for example, during the discussion a mistake in my comparison and evaluation approach is discovered which makes my results meaningless? Although I discussed my approach and everything I did with my advisor (postdoc not the prof), yet I still fear that I might have done something wrong and then everything collaps.

This should not happen unless:

  • The mistake is blatantly obvious and something you should have really known better. And with blatantly obvious, I mean something that somebody who has not even studied computer science or a related field could easily spot. Even then you may have chances, if the rest of your work is appropriate – almost everybody brainfarts now and then.
  • You made not only one mistake but a lot of big mistakes.
  • It becomes obvious that you deliberately ignored that mistake, to avoid being stuck or to get “nicer” results.

(In the first two cases, your advisor is in big trouble, too.) The point of the master thesis is that you should demonstrate that you can investigate a scientific question under supervision (or something similar – check the regulations, if you wish to know). One mistake does not change this.

Moreover, in some examination regulations I am aware of, there is a procedure for the case that some important but localised flaw is detected in your thesis. For example, you could be given a month to amend your thesis.


How would one fail a master thesis defense?

I have not experienced or heard of such a case but from what I have gathered, you pass if you:

  • Give a talk about your thesis.
  • Be able to answer questions about it.
  • Are not detected to have been cheating.

Even if you suffer from a mental breakdown due to nervousness or similar, you probably can repeat the defense – at least with any reasonable examination regulation and examination committee. I am aware of one case where somebody had a nervous breakdown for understandable reasons¹ and the examination board let him repeat the exam. If you look into your examination regulations, there are probably some clauses that allow the examination board to do some things at their own discretion in exceptional cases.


Be aware though that being very difficult to fail does not make the defense unimportant. A bad defense may seriously (and in particular more than nominally) affect your thesis degree, which in turn has a huge impact on your total degree. In particular having passed a thesis with the lowest possible degree (or something close to it) is something you definetely do not want to have in your vita².


¹ It’s very complicated, but you might compare it to the following: In the middle of the defense, somebody who was the defender’s girlfriend until six months ago enters the room being obviously pregnant in her ninth month.
² Unless you are in one of those few disciplines where this is the norm.

  • You really calmed me down. A nervous breakdown means crying or what do "you" mean by it? – Jack Twain Mar 14 '15 at 22:06
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    Why are you putting you in quotation marks? It’s not my story; if that’s what you were thinking. Nervous or mental breakdown here can mean all sorts of symptoms that make you psychologically incapable of holding your defense. – Wrzlprmft Mar 14 '15 at 22:16
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    @JackTwain: 1) I am perfectly calm and what you describe is not a good explanation to use quotation marks at all. 2) About 40 % of the final exams in law in Germany are passed with the lowest grade – though there is no thesis involved in this. Also, obtaining a doctor of law with the lowest degree (rite) is not unusual (though I have no numbers for this). – Wrzlprmft Mar 15 '15 at 10:00
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    Great answer, however note that grading of the thesis or the thesis defense is no globally applicable. – posdef Mar 15 '15 at 12:07
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    The only person I've ever heard of to fail his thesis defense (Austria) in CS was a guy that started an answer to "What is object oriented programming?" with "Umm.. good question!" and everyone wondered ever after how the hell he cheated his way through all the exams leading up to the defense. It's pretty much impossible to fail your exam. I'd say it's more something to look forward to: Discussing a topic you're intimately familiar with some colleagues should be fun. – Voo Mar 15 '15 at 14:07
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Evaluation criteria varies vastly, not only across different countries and cultures but even amongst different institutions within a country.

The only way I can imagine anyone failing a thesis defense here in Sweden is if you have a mental breakdown during presentation or questioning.

Alternatively if the defending student has plagiarised parts his/her work, that would also be a likely fail but otherwise, if you are allowed to defend, then you have practically passed already.

  • I believe the academia atmosphere in Sweden is similar to that in Germany. What does 'mental breakdown' mean? Gone mad?! – Jack Twain Mar 14 '15 at 12:47
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    Mental breakdown would stand for a blackout where you transiently forget everything you know due to being overly nervous. Likewise, in Ireland, where I did my PhD, if your supervisor allows you to defend your thesis it would take unlikely catastrophic circumstances to fail the actual examination. – Miguel Mar 14 '15 at 14:01
  • @Miguel thank you. That gave me some kind of relief and security. – Jack Twain Mar 14 '15 at 15:13
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    @JackTwain The possibility of being wrong is always present in research, and is a fundamental part of doing new stuff. You are exploring uncharted territory. Until your ideas have over the years been tested by others or applied to different problems you cannot be certain of the relevance or even correctness of your results. Only a tiny fraction of the original research literature enters the textbooks. You have done what you must: make sure that to the best of your knowledge and ability your thesis is a sincere record of your research. – Miguel Mar 14 '15 at 19:29
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    Just to add: there is a grade associated with a Master's defense, so it is possible to get a low grade, if you don't present or answer questions well. But actually failing is very unlikely, as this answer explains. – Lubo Antonov Mar 14 '15 at 21:00
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It's pretty rare for a student to fail the defense of a master thesis in the Swedish systems, but I have seen a few over the years. The three most common reasons include:

  • Did not show up to defend the thesis (AKA: Lose on walkover)
  • Doesn't know the material of the thesis (AKA: Didn't write it)
  • Unable to hold a discussion about the thesis (AKA: hid in a corner)

Note that unlike a PhD thesis the professor does not have lot of skin in the game. Having a PhD student fail a defense is extremely embarrassing and can end the career of a professor. Having a master student fail a defense isn't considered such a big deal.

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    "can end the career of a professor"? Haven't heard of that, ever. – Dirk Mar 14 '15 at 15:35
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    @Dirk good. Now you know so you can make sure that doesn't happen with your PhDs :D – Jack Twain Mar 14 '15 at 15:36
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    Actually I still doubt that this really has ever happened. – Dirk Mar 14 '15 at 15:38
  • @Dirk would you fail a master student in his defense if turns out that he did a mistake and the results of the thesis are as a result useless because of this mistake? Suppose that this gets discovered only during the defense, and it was an honest mistake. – Jack Twain Mar 14 '15 at 15:40
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    Dirk: I know of two cases, one in nursing and one in molecular biology over the last decades where a PhD student was recommended to defend and failed. In both cases this ended the research careers of several people involved. – pehrs Mar 14 '15 at 15:49

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