There are lots of statistics about the general experience of the PhD viva – but we can’t combine them to find out the probability of a particular outcome.
Want to know how likely it is you’ll have a four-hour viva with major corrections and three examiners instead of two? Sorry, I can’t tell you and you can’t work it out.
There are lots of patterns of experience. Vivas tend to result in minor corrections. They tend to be longer than two hours. But to combine these and other details meaningfully and make predictions we’d need to know a lot more.
PhDs and vivas are unique: they follow patterns, but are always different. The patterns can show you what you can do to be ready in whatever situation you find at your viva.
You don’t need to work out the odds of success: instead work towards being ready to talk with your examiners and prepared for passing your viva.
