Quote from EricEnfermero
The chance of passing, for a US-educated, first-time tester is ~85%. The number of questions you receive doesn't enter into that equation.
Actually, Kaplan says it does. By the time you get to 265 questions, your chances of passing drops to 50 percent. But, that still means you have a 50/50 chance of passing.
The way they explain it is this: there are a series of questions that are both above and below passing level. Above passing level questions are more difficult. So it all depends on when you can put a string of right answers together for the more difficult above passing level questions, or not.
If you do that early in the test then, that's when it shuts down. By the same token, if you've dug a hole with too many answers below passing level then it shuts down. You can still fail if you shut down at 75 but, chances are, you probably put that string of difficult right answers together early on.
If you're somewhere in between where you're getting some of the above passing level questions right but not enough of them to pass then, the test keeps giving you chances to put the required string of difficult right answers together up to 265.
This is why your chances of passing can diminish somewhat the further you go because you probably haven't put that string of difficult right answers together yet. You can still do it, and a lot of people do ... but, the chance of success does drop.