[ska]

Oh, good point, the UK programs I know of are notably ligher in this regard (and PhD shorter) though they do generally require a 1st class honors (honours, i guess!) degree in subject, which includes "tripos" which is roughly equivalent. So in some ways a higher bar for undergrad matched with a lower bar for grad.

At least that's the theory - I don't know if in practice it holds up; most of the grad students and later I knew from that system came from oxbridge which has a number of quirks.

[g_p]

The difference I tend to see is that the outcome of the UK viva (oral) examination is far less of a foregone conclusion, and can still be quite traditional in that students are expected to be able to have a broad and well-informed discussion about their wider field and the context of their work. The thinking is that they will (if meritous of a PhD) have a certain level of expertise, and thus be able to have a discussion with their external examiner (a distinguished and recognised expert) as a peer.

My experience of it was that if you are genuinely knowledgeable and approaching being an expert in your field, it is an enjoyable experience, and just like having a (longer than usual, but not uncomfortably long) conversation with someone about a topic that you both share a deep interest in. There is nothing to worry about, as you can have a nice discussion about an interesting topic, and share interesting ideas etc.

I'm not sure if it's a lower bar for grad as such - I think it's got fewer "formal" requirements, and far more informal requirements. The most common way to "fail" is to simply not submit the thesis.

[twic]

I don't know anyone who failed their viva entirely, but it's standard to be asked to make corrections to the thesis after it. Getting passed without corrections is a significant achievement. Those corrections can relate to weaknesses in your general knowledge uncovered in the viva: if there is something the examiners think you should know about, and you don't, you can be asked to add it to the thesis.

My impression was that someone failing their viva was seen as a serious failure on the part of their supervisor, who should not have let them submit without being more prepared.

[ska]

> UK viva (oral) examination is far less of a foregone conclusion,

That matches my limited experience with UK, although I've seen north american ones without a foregone conclusion - seems really dependent on institution.

> The most common way to "fail" is to simply not submit the thesis.

I think that's true everywhere, lot's of people just don't complete. I've heard somewhere that the "ABD" (all but dissertation) rate in US is nearly 50% at 10 years, if you go across all disciplines.