Chris,

Here is how PMI describes this in the PMI-ACP Handbook:

"The PMI - ACP exam is comprised of 120 multiple - choice questions. Of the 120 questions, 20 are considered pretest questions. Pretest questions do not affect the score and are used in examinations as an effective and legitimate way to test the validity of future questions. All questions are randomly placed throughout the exam ."

As PMI says, the pretest questions do not affect your score at all. They are excluded from calculating your final score and exam result.

I keep reading there are 20 pre-exam questions on the test, how do these work into your score? For example, if you got 100 questions right and 20 wrong, but all 20 were the 'pre-exam questions, would your score be 100% or 83%?

What if you got those 20 right but another 20 wrong, would your score be 80/100 (80%) or 100/120 (83%)?