In France, referees (external) allowed the oral presentation (public defense) only if they are satisfied with the quality, format of the thesis. Once public defense is allowed, it is rare that degree is refused only on the basis of poor presentation or some unsatisfactory answers.

1, The simplest circumstance to describe is the PhD 'scholar' being caught out at plagiarism.

2. The 'scholar' may be so poor at spoken English, that he/she cannot answer any questions posed.

3. The 'scholar' may be eloquent, but be unable to satisfactorily answer the questions that are posed about his/her thesis.

4. There may have been some doubt about the standard of the thesis, and the candidate is unable to swing the committee verbally.

5. Nota Bene: The PhD thesis is deemed not to be a significant, original contribution to humankind's knowledge.

6. The thesis was written poorly and a simple edit cannot bring it up to standard, so there is no thesis defense.

7. The thesis has some minor problems that the candidate refuses to address.

8. The research work was so poor that it cannot be salvaged and no thesis defense occurs.

Although a candidate can submit his/her thesis against the advice of the Adviser, this is rare. Thus it is normal that the Adviser has approved the thesis.

So, I feel that the final role of the Adviser is only to cast a final vote if the committee is divided. In general, however, things would not go to a vote, but a unanimous decision would be striven for, based on discussion.

1. poor presentation skills

2. contradictions in findings & Presentations

3. non reliability of data presented.

4. grammatical mistakes in thesis as well as presentations.

5. no or negligible contribution in existing body of knowledge......

We have now collected 12 bullets, because Parag's #5 and my #5 are the same. Number 5 is, in my experiences, the most problematic as it is open to expert opinions on originality and significance. Of course, the adviser is also being 'examined', because he or she has been the promoter of the PhD thesis. The best role for the adviser to play at this stage is to be supportive but not illogical.

Interesting answers! Our University though, has now put up so many barriers (to be overcome by the candidate), in the form of presentations almost every year, that its difficult for a candidate to manage to fail in open defense :)). In spite of this, if the candidate fails in the open defense, reasons have to be very strong like;

1. very low confidence in presenting the work before the panel (reasons may be varied, many have been stated above)

2. not being able to advocate his / her own work

3. the guide or supervisor, not being very supportive (verbally and non-verbally)

4.everything goes wrong, from the beginning to the end (very rare, but I have seen it happen !)

In France, referees (external) allowed the oral presentation (public defense) only if they are satisfied with the quality, format of the thesis. Once public defense is allowed, it is rare that degree is refused only on the basis of poor presentation or some unsatisfactory answers.

As Yasir points out, pre-presentation quality checks prevent angry or tearful vivas. The oral becomes "business as usual" and is a mere formality and a milestone to celebrate.

I agree with Yasir on that poor presentation or unsatisfactory answers to some of the questions may not be allowed to weigh too much on the final decision. Similarly Ian's point about plagiarism may not be too serious because these days PhD candidates have easy access to plagiarism check software and can easily mange it prior to submission. Some other points like contradictions within the document are serious thing but I think that is where the responsibility of the advisers come in. An adviser should not allow the submission of such a thesis.

Besides all that, I'm still a bit confused about how to measure whether the thesis being examined contributes to the body of knowledge significantly. It's such a relative phrase isn't it? And don't you think an examiner, if determined to do so, can always win an argument that a particular thesis doesn't contribute enough?

The thesis-book itself must contain visible evidence of the work being both 1) original and 2) a significant contribution to knowledge. Otherwise no PhD. The best way of ensuring the PhD is original is to ensure that originality is satisfied for every component (e.g. question, subquestions, subanswers, measurements, data, analysis, thesis-theme, conclusions, references etc.). Also spell out clearly in the thesis-book how the work is significant and why it is a contribution to knowledge.

That was on the dot :))

Intersting question. Can one or should one fail a PhD? I guess the level of the assessment matters. If a thesis is flawed, weak and is not progressive, surely these should have been picked and addressed firstly by supervisor and secondly by examiners. When it is at the defense stage, is it not too late? What does it say about the quality of supervision? I would like to think a failing PhD speaks volume about the institution and supervision.

I would not put much on language eloquency, especially if it is not student's first language. It is the duty of the supervisor to ensure that his/her student is comfortable during the defense and language accommodation is most definatley one of the prerequisites. The student must be eloquent in speaking about his/her work. Lack of perceived impressive vocabulary, especialy second or third language is by no means and indication of low intelligence or lack of knowledge of the subject or phenomena.

However, for the first part of the question, I would like to know whether the student has developed and is able to critique his/her final product. Whether the student is able to speak outside the thesis and tell the panel, knowing what he/she knows now, what will he/she do differently to address his/ her question? Knowing what he/she knows now, would he/she ask a different question? Why?

the discussion seems to be interesting ...

Some thing I would like to add on. recently my colleague was attended a PhD viva at University. The presentation skills of candidate is so poor (may be due to the candidate belongs to tribal area), but the data & analysis is of worth quality. the chairman of committee told that ... since the thesis has been accepted by both the referee with good score... we cannot reject the thesis...

What I mean to say is performance in open defense can be sometimes neglected in case of quality thesis.

so I do agree with Ian kennedy that....

"The thesis-book itself must contain visible evidence of the work being both 1) original and 2) a significant contribution to knowledge. Otherwise no PhD. The best way of ensuring the PhD is original is to ensure that originality is satisfied for every component (e.g. question, subquestions, subanswers, measurements, data, analysis, thesis-theme, conclusions, references etc.). Also spell out clearly in the thesis-book how the work is significant and why it is a contribution to knowledge."