I realize I made a huge mistake in my thesis and am not sure what to do. I'm defending very soon (days away). What should I do?



I realize there is a somewhat similar question posted, but my question is different in that I found a pretty big mistake in my thesis. It's such a big problem, it changes my results. I almost wish I hadn't noticed, and been so careful to go back and check every thing, because I really don't know what to do about it except fix the errors/interpretation errors and discussion (today). I defend very soon (in days). It's possible that my committee won't notice it, but I feel like the guilt might drive me insane. I'm worried that my chair noticed it in the past, but they didn't correct me because they feel I'm incompetent (which I feel in ways I am when it comes to stats). Should I re-write it and let my chair know and ask what to do? I need to defend soon in any case. I wonder if I could just present as though I'd already corrected it and e-mail the revised manuscript beforehand. I'm just not sure how they would perceive someone who overlooked such a obvious mistake. Any advice would be appreciated.


Posted 2017-03-26T20:20:03.370

Reputation: 796

98Talk to your supervisor as soon as possible! – dsfgsho – 2017-03-26T20:45:32.950

117The most praise I ever got was for pointing out flaws in my thesis during the defense. It shows integrity, which is the most important quality to have in research imo. – Minix – 2017-03-26T20:51:12.717

32Is it a PhD, MSc or BSc thesis? – Dmitry Savostyanov – 2017-03-26T20:53:43.717

8It's a MS thesis. As far as I've heard, the only time anyone has failed (recently) was during their proposal, which makes me think the program in general is pretty willing to work with student/allow them to make corrections (I hope!). I am contacting my supervisor immediately. The issue is that I misinterpreted the way an instrument was scored (it's an archival data set). Anyway, I'm definitely panicking! – Gellen – 2017-03-26T21:31:04.177

65Take a deep breath, put it as far from your mind as possible, and go to bed early. None of this is stuff where being in a panic helps. In the morning, talk to your supervisor as early as you can and ask her to go over your concerns first thing in the morning. It can very well happen that it's you misinterpreting the data right now and that there isn't a mistake at all (it happened to me a good six weeks after I'd defended, with the corresponding paper under referee consideration). If there is a mistake, it's not something that a weekend panic will help solve. – E.P. – 2017-03-27T00:32:01.880

2Thank you! I will try. I probably won't get to meet with my advisor tomorrow because I have class/meetings all day, but hopefully if I explain what I think went wrong they'll be able to verify. – Gellen – 2017-03-27T02:34:01.007

39@Gellen I'm very interested in knowing how things turned out. Please let us know! – solalito – 2017-03-27T05:43:02.377

5My phd thesis has an error on it. Nobody noticed it yet (since 2012). It doesn't invalidate anything, the theorem is still true and all, so it is minor, in comparison. My point being: stay calm, address it quickly and honestly... errors happen.... – Fábio Dias – 2017-03-27T22:26:54.980

11I discovered a major error in my PhD thesis a few weeks before defending. In the end, it only made my thesis 15 pages shorter. – JeffE – 2017-03-27T23:18:16.330

11@solalito For your benefit, one of the comments OP posted: "Hi guys, yea, I was able to correct my thesis and send it to my chair via an all-nighter. I'm sure they were annoyed, but they reviewed it and suggested some wording changes here and there.I can't imagine that my thesis is anything remotely like a dissertation, but it's still been challenging due to ADHD (I overlook details all of the time!) and my father passed away last semester unexpectedly. I wanted to go straight into a PhD program after this degree, but I'm delaying a year since I think I need to improve myself in some areas." – Abdul – 2017-03-28T21:15:13.310

1Be honest with your supervisor and examiner and tell them that you found something wrong and you are going to fix it. Finally, I wish you the best with your viva. – sky-light – 2017-03-29T12:45:12.223

9Please read about impostor syndrome. It sounds like something you should be aware of. I'm glad you got some great answers and suggestions, and I'm sure you'll be okay. – Joe – 2017-03-29T15:29:15.850


@solalito Some new feedback from OP here: "Yea, it changed my results, BUT it made them better. It took me all night to edit my thesis, but I sent the revised copy to my chair this morning, and they asked me to reword some things here and there, but that's it."

– Marc Ranolfi – 2017-03-30T03:29:13.593


If it happened to Poincare, it can happen to you. Note that he went on to be an epochal figure. So can you. https://en.wikipedia.org/wiki/Henri_Poincar%C3%A9#Three-body_problem

– Jared Smith – 2017-03-30T13:24:57.300

1To publish something hiding a known error is UNACCEPTABLE academic conduct. How can we ever benefit from research if we can't trust it's integrity? The science is being undermined. If you are truly interested in the pursuit of knowledge, it is an obligation to report the error. The general public already has enough problems trusting academic research. Sometimes you have to do the right thing, even at expense to yourself. Bad results won't ruin you, but bad integrity will. – Airhead – 2017-03-31T18:21:11.883

After my PhD defense, I got congratulated by a professor who was present at the defense just of out curiosity, and at the same time she pointed out a mistake in on of the equations. When I looked at it at home, it turned out that in one of first pages of my work I wrote an utter nonsense. Later, she said to me what many people are telling you here: don't worry, this happens to all of us :) – BartoszKP – 2017-04-02T11:17:34.413

3@Airhead Yes, I did tell them about it. I'm sure there are a lot of people that opt to not tell, and get away with it. After the panic settled a bit, I knew that wasn't a option for me. – Gellen – 2017-04-03T20:54:17.807

6@BartoszKP Thanks! I'm still ruminating about the mistake (though I passed the defense last week). It's comforting to know that this happens more regularly than I thought. – Gellen – 2017-04-03T20:58:41.250

4@Joe Thanks! Yeah, I've been dealing with impostor syndrome since I started my program. It's certainly undermined my confidence/performance at times, so I imagine it's done the same to countless other students. – Gellen – 2017-04-03T21:03:28.727

2I realize this is an older post, you've defended by now. However, I want to commend you on your integrity. I have way more faith in people who play devil's advocate with their work and point out its flaws than those who don't. – mas – 2017-04-04T04:37:55.743



The thesis and thesis defense is less about having the results you wanted to have, and more about demonstrating that you know how to do good quality research and can work on that somewhat independently. It's about figuring out what questions to ask and what methods can be used to find the answers, and then applying those methods to come up with answers. What the answers actually are is not as important [for the purposes of passing a thesis] as the process you took to get those answers. Your discovering this issue and taking prompt action to fix it shows attention to important details and integrity in the knowledge-discovery process. Sure, it would've been better if you'd caught that earlier, but you've caught it now, before your defense, and you're rewriting the discussion and conclusions to reflect your best analysis of the data.

In my opinion, your having found this and your efforts now to promptly fix it say more [positively] about what a thesis is supposed to evaluate than most completed theses.

Don't panic. Talk to your supervisor and committee. Tell them what you found. Revise your document to reflect the new understanding. Maybe you'll have to delay the defense a bit, but more likely you'll present at the same time and talk about what you found; the committee might require you to deliver a revised document [some weeks after the presentation] reflecting that before they sign off. That might take you some time to do but it should be OK, and will leave you with work you can feel is more solid.

Kudos to you for finding the issue and having the integrity to stand up for it. This should help you in the long run and the core evaluation at issue here, at the cost of some extra work to revise and maybe some scrambling to re-practice your revised presentation.

Edit: Congratulations on passing!


Posted 2017-03-26T20:20:03.370

Reputation: 2 651

8Thanks, you're perspective makes me feel a little better! It'll definitely cost me some sleep in the coming days to prepare, but it's worth it. Hopefully my advisor and committee won't be too annoyed. – Gellen – 2017-03-27T05:06:36.687

1Just wondering, do you have a source for the information in the first paragraph of this post? – jrh – 2017-03-27T19:55:52.533

5I think you need to be careful not to generalize in your first paragraph. Where the thesis and thesis defense is most common (or required) is for a PhD - in that case if an error invalidates all or the majority of the stated contributions, graduation is unlikely. The fact that the poster is completing an MS thesis should be placed in the question itself of in your response. – user58322 – 2017-03-28T08:19:22.553

@user58322 Not to ask a similar question again but I still don't quite understand the difference here: Why would an error invalidating the majority of the stated contributions make graduation unlikely for a PhD, but would not effect graduation <as much? at all?> for a thesis track MS? Is it because an MS thesis is only a grade but a PhD thesis holds more weight? Does it just vary based on advisors / schools? – jrh – 2017-03-28T11:34:39.350

4@jrh A MS thesis is research with training wheels, this is a way for you to learn how research is conducted and show that you have mastered the skills. A dissertation at the Ph.D. level is much more about demonstrating your ability to independently drive the field forward. The test there is not do you know how to conduct research, but can you successfully apply those skills to an appropriate problem. – Ukko – 2017-03-28T14:30:11.193

4@jrh Ukko has the right of it. While making some level of sufficient contribution is necessary for a PhD, I have not seen a similar strict requirement applied for a MS. Indeed, in the US, generally the exact same Masters degree is given to those students who take the coursework option, project-based (thesis) option, or do a direct PhD and receive the MS after finishing qualifiers. Novel contributions (and from them published papers) are great and have significant impact on the success of a later PhD application, but are above and beyond the minimum required to graduate with a MS. – user58322 – 2017-03-28T16:47:16.933

1@jrh how would he be able to find a source for his own personal opinion and experience? I think you took it a bit more authoritative then it was conveyed as. The author's just giving his opinion of a thesis. :) – The Great Duck – 2017-03-31T00:28:08.497

@TheGreatDuck I guess was hoping for some sort of official academic guideline or something, I wasn't really aware at the time that it's mostly a matter of opinion. I guess I still haven't really figured out how the thesis courses (with relatively vague requirements) fit into the university grading system -- It's not like classes where you get a percentage grade on an exam / project, and apparently it's not like a job where you have to do everything you proposed, and the results are expected to be competitive or the project failed... it's somewhere in between? I must be missing something here. – jrh – 2017-03-31T02:23:16.230

1@jrh well it is probably still graded like a normal course. I just mean to say that like with any course it's up to the faculty and professor in charge of it to determine the policy. Therefore, anyone can have their own competent opinion of a thesis so long as they have a decent amount of experience. It's not different than any other course. It might just be that some people choose to teach it one way or another. It's not a set in stone thing. – The Great Duck – 2017-03-31T18:44:06.730

2@jrh My program uses the thesis as mostly a learning experience for the most part. They didn't expect for me to have made 0 methodological mistakes, but my committee pointed them out and discussed them with me. That being said, there are people who have failed during the proposal if their project is especially unoriginal and basic. So, in my program anyway, there is an expectation that you'll do something more advanced than you might have at an undergraduate level. – Gellen – 2017-04-03T21:11:50.877


Get off of Stack Exchange and contact your advisor, right now. He/she is the most qualified person to help you understand what is going on and what to do about it.

It's possible you might have to delay your defense in order to fix it. That would be unfortunate, but not the end of the world.

On the other hand, if you know about a serious error and defend anyway in the hopes that your committee doesn't notice, that is deeply unethical. We are talking "kick you out of grad school", "revoke your degree years later" unethical. That is not an option. Forget about it.

It seems to me unlikely that your committee knows about the error but is intentionally ignoring it in order to "trap" you. That would be very inappropriate behavior on their part, and I've never heard of it happening. There would be nothing for them to gain by doing so. And even if this were the case, pretending you don't know about the error would only make things worse.

Nate Eldredge

Posted 2017-03-26T20:20:03.370

Reputation: 83 799

16Thanks Nate, I've e-mailed them. I know they probably won't check until tomorrow morning (they don't answer emails on the weekends). I definitely won't try to defend and not tell them! I think I'm just panicking and thinking illogically. – Gellen – 2017-03-26T21:40:18.687

15its just a MS thesis ^^ no big deal. – Rüdiger – 2017-03-26T22:33:01.090

17@Rüdiger These people are going to be OP's academic references, for one thing, and given that there is an ethical question here, resolving that incorrectly could affect a career very negatively, could it not? – msouth – 2017-03-26T23:48:24.330

1I'm pretty sure that if my U declared they revoked my degree it would do nothing. I have original papers and sealed transcripts and it would convince a potential employer well enough. With 10 years job experience under my belt I don't think they'd care anyway anymore. – Joshua – 2017-03-27T01:16:07.230

4@Joshua depends on the field, career path, degree, etc. I worked a job a while back where there are specific requirements for positions for legal and insurance reasons. One woman had to be let go because she didn't have the right degree even though she had plenty of experience and knew what she was doing on the job. – Todd Wilcox – 2017-03-27T02:21:34.090

2"It seems to me unlikely that your committee knows about the error but is intentionally ignoring it in order to "trap" you." I had committee members saving hard questions like that for the defense, but I agree it seems unlikely that's what's happening here - especially for an MS thesis. – WBT – 2017-03-27T03:45:40.753

7@Rüdiger Just wondering, could you explain why this being a MS thesis makes a mistake like this "not as bad" as a mistake in a PHD thesis? I hear stuff like "It's just a MS thesis" somewhat often but I don't really understand why they're not as much of a "big deal". For some reason I've heard sky high expectations of MS theses and rock bottom expectations presented with equal validity and not much reasoning as to why. Even between departments at my own school I hear both sides... – jrh – 2017-03-27T13:49:06.163

1@WBT Committee members will sometimes try to think about a question the student can't answer in order to test what they'll do about it (hopefully say something like "I don't know, but this is how I'd go about finding the answer ..."). Or if the method has a weakness then committee members might ask you to explain in what situations your result is valid and in what situations it isn't. However, if you answer well, these questions don't affect your grade negatively. I've never heard of a committee member ignoring a real mistake in order to point it out in the defense. – Sumyrda – 2017-03-27T18:09:31.260

@jrh MS thesis or PhD thesis both don't really matter. How many lives or dollars depend on it? – emory – 2017-03-27T19:24:20.187

2@emory it might matter to people that flunk out of their graduate program, e.g., from this answer: "We are talking "kick you out of grad school", "revoke your degree years later" unethical.", in that case the dollar and time loss can be very significant. – jrh – 2017-03-27T19:32:58.680

1@Gellen: When the dust settles, don't forget to accept an answer! :) Best of luck to you. I do not envy your situation. – jvriesem – 2017-03-27T19:54:25.127

2@jrh don't lie about it, but don't sweat it too much either. No one is going to die b/c this mistake. OP might be able to defend the thesis with mistake unfixed. Address it in the conclusion under "Suggestions for Further Research". The thesis not not meant to be the final word. Perhaps OP will need to spend more time in school but perhaps not. Any school that would revoke degrees for being less than perfect is not a school I would want to be involved with. – emory – 2017-03-27T20:04:58.447

2@jrh it's a difference whether a mistakes makes 4 months of work useless or 4 years of work. you just can't compare a msc thesis with a phd thesis... most msc theses are just a joke when compared to a phd thesis – Rüdiger – 2017-03-27T20:56:08.480

25Hi guys, yea, I was able to correct my thesis and send it to my chair via an all-nighter. I'm sure they were annoyed, but they reviewed it and suggested some wording changes here and there.I can't imagine that my thesis is anything remotely like a dissertation, but it's still been challenging due to ADHD (I overlook details all of the time!) and my father passed away last semester unexpectedly. I wanted to go straight into a PhD program after this degree, but I'm delaying a year since I think I need to improve myself in some areas. – Gellen – 2017-03-27T23:12:54.233

2@Gellen It is great that you noticed and fixed it on time! Depending on the issue, if you find it appropriate, you may even mention (written or in the defense) that care is required in order to avoid such mistakes. Furthermore, that mistake may not be so obvious as you think, otherwise your committee should have seen it as well (here I agree that it is unlikely that they would let it go on purpose). – iled – 2017-03-29T04:49:04.030

2@iled Yes,luckily no one brought it up during the defense. I don't think it would have been noticed, but nevertheless, I'm glad I did notice it. I'll certainly be exceptionally careful next time after this experience! – Gellen – 2017-04-03T21:16:09.490


This happened to me. I found an error in a complicated mathematical proof in the appendix to one of my papers. As I flew home to defend it I was fixing the mistake on the plane. In the defence, I told them about the error. They told me to fix it and awarded me the degree. This was a formal political theory paper; I doubt if they even read the appendix, but I'm glad I told them.

Unless this mistake blows away your results, it's best to be honest. (Actually, it's best to be honest in any case. There are lots of bullshitter academics out there; don't be one of them.)


Posted 2017-03-26T20:20:03.370

Reputation: 411

32Yea, it changed my results, BUT it made them better. It took me all night to edit my thesis, but I sent the revised copy to my chair this morning, and they asked me to reword some things here and there, but that's it. – Gellen – 2017-03-27T23:15:32.283

13No, especially if it blows away your results ! Do you really want an erroneous outcome to remain, and quite possibly screw up someone else who depends on your research to further his? – Carl Witthoft – 2017-03-31T12:05:06.680


I'll add a suggestion to the excellent answers provided already:

When we find an error in our proof or even our claims - especially in something as significant in our lives as a these (even if it's an M.Sc. thesis) - we tend to believe that everything is ruined and the research is useless. It's really not. Even if you can't fix it in a day. I would go into details regarding why that is, but that doesn't matter now.

The important thing to remember is: Don't make the reporting of the mistake the focus of your thesis presentation. You should definitely be fair and open: When you get to the part which directly relies on the error, tell the committee that as you were preparing for your defense, you find a mistake in that claim / in the proof of that claim. Don't start going on and on about the mistake and how you made it and how it invalidates everything; make your presentation like you would if you hadn't found your mistake, and when you get to where the mistake actually happens, that's when you say what the mistake was instead of presenting the erroneous argument. Let the committee decide if they want to focus on it or whether they would rather hear the rest.


Posted 2017-03-26T20:20:03.370

Reputation: 16 152


Andrew Wiles' famous proof on Elliptical Curves also proves Fermat's last theorem 356 years after Fermat proposed it. The 1993 proof contained an error that took Wiles over a year to fix with the help of his assistant Richard Taylor. Even the greats make mistakes or overlook things. This is why papers are peer reviewed in the first place. Even with the mistake, the original proof was valuable as it showed innovative approaches to the problem.

Robert White

Posted 2017-03-26T20:20:03.370

Reputation: 231


If you could fix the thesis in under a day, it wasn't a major error. In the words of Benjamin Franklin "When in doubt, tell the truth. It will amaze your friends and confound your enemies." Just be glad for word processors. Back when I was in college, I had to type out my papers by hand on a typewriter, and created the graphs using rulers, triangles, and Rapidograph pens.

Bradley Ross

Posted 2017-03-26T20:20:03.370

Reputation: 181


First, Speak to your advisor immediately. That person is in the best position to guide you. Second, realize that the most valuable stock-in-trade in academic life along with competency is integrity. Research mistakes WILL happen, that's a fact of life and the imperfect world we live in. [Albert Einstein did not get General Relativity right the first time he published it and save for WWI, experimental data would have disproved the incorrect version of GR.]

Needing or waiting for someone else to point your error out (especially since you discovered it already) speaks poorly of both one's competence AND integrity and surely you don't want that outcome.

If it's too late to amend the thesis prior to its defense, it's better that they learn from you of the error than having someone else point it out. That would demonstrate both your competence AND integrity.

Ken Clement

Posted 2017-03-26T20:20:03.370

Reputation: 209


A good academic committee will recognise the positive significance of a candidate who proactively checks their work and takes errors seriously. They would see it as a plus for you, not a minus, whatever the effect on your thesis, because the thesis itself is a tool to assess you as a researcher in the field, and this action will indeed reflect well on you. (And you won't have to worry about someone else noticing it in future!)

Write them a formal note explaining what you found, and your initial assessment of its impact - extra time, any changes to the paper, etc - and tell them what you'd like (an extra week or month to rewrite that section, or update it to fix the issue, or to consider if any other part is affected and needs changing as a result).

Be matter-of-fact and cordial - and have a verbal chat with your supervisor in which you show him/her the note you have drafted and check it looks OK to them. That also gives your supervisor a heads up so they don't look foolish or caught by surprise, and a chance to give any other advice.


Posted 2017-03-26T20:20:03.370

Reputation: 686

Hi! Thanks for your advice. That's pretty much what I did and it worked out fine. I passed my defense last week!! – Gellen – 2017-04-03T20:49:27.783


In independent study as an undergrad I reviewed draft MS and PHD papers for Math errors. Every paper had some error or errors, some were minor, and some were major. It was never a big deal unless the grad student got defensive. Accepting the criticism and moving on was part of the process. The students who positively engaged with my adviser to understand the flaws and gain a deeper understanding were really appreciated by their adviser and the committee.


Posted 2017-03-26T20:20:03.370

Reputation: 11