In one of my PhD thesis chapters, I have a derivation of a theory that I have proposed in the paper. I just found out that I have made an error in the calculation, and my derivation is flawed. The chapter is yet to be submitted in a journal, so it has never been peer reviewed. I never saw the flaw before this. Do I bring it up during my defense? And what do I say if the committee asks me about it? Can that have a negative outcome on my defense result?

I am feeling scared now!

Should I mail my advisor? My defense is on Monday afternoon and I don't know what to do!

  • 1
    Have you talked with your advisor about this?
    – Drecate
    Commented Nov 23, 2019 at 19:44
  • @Drecate Just figured it out today. Not yet talked to her.
    – Aman
    Commented Nov 23, 2019 at 19:47
  • Is there enough time to recalculate and do a new derivation in time for the defence?
    – Poidah
    Commented Nov 23, 2019 at 21:06

2 Answers 2


First, tell your advisor immediately. Your defense might need to be rescheduled. Suggest that if you think it wise.

Next, of course, try to provide a correct derivation.

If you have to go to the defense in the current state, yes, admit and point out the error and state that you are working on a patch. The committee might let you finish as is and clean up the problem later. They might also delay your finish until you have a correct result (or proof that it is not correct). I doubt that this is grounds for complete failure as it would be if the error is pointed out by someone else.

But your advisor might override any of this advice. That is your best source.

I've been on a final defense committee where we decided the work wasn't ready due to some flaws. The candidate just had to go back to work and we scheduled a future date. But it turned out that the meeting itself was valuable for the candidate as he got some feedback that helped him to the end.

  • 3
    I completely agree with "tell your advisor immediately", but let me amplify that a bit: Tell her everything that's relevant. That includes not only the fact that you found an error at such-and-such place in your thesis but also the exact nature of the error, how much of your thesis is affected by this error (do a lot of later results depend on the flawed argument?), whether you think the proof can be repaired, and (if so) how long it's likely to take to repair it. Commented Nov 24, 2019 at 3:08

In addition to Buffy's answer: How bad this is also depends a little bit on how central the proof is for your work: Does it severely influence the main hypotheses of the work? If so, rescheduling the defense is necessary. If it is only of minor importance, there might be a possibility to correct this after your defense: At least at my university, this possibility exist for exactly the purpose of correcting minor mistakes, and the committee frequently asks the PhD candidate to make use of this option.

But yes, talk to your advisor about it.

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