The scoring of the Praxis Core PPST proceeds according to a strict protocol. In the multiple-choice sections, your raw score is the number of questions answered correctly. There is no distinction between unanswered questions and questions answered incorrectly. This means that you should always make your best guess on Praxis Core PPST multiple-choice questions. There is no advantage to skipping over the questions you find difficult. The raw score from the multiple-choice questions is converted into a scaled score according to an algorithm that accounts for the relative difficulty of the test.
Your constructed responses on the Praxis 1 PPST are scored by two trained scorers in consultation with a detailed scoring rubric. Each scorer assigns a grade; if the scores differ by a certain amount, a third scorer is brought in to mediate. There is no cause for concern over subjectivity in the grading of the Praxis Core PPST; the process of assessment has been standardized entirely. Finally, some of the multiple-choice questions on the exam are pretest questions, which do not contribute to your score. These questions are included to see if they should be a part of future versions of the Praxis Core PPST. You will not be able to identify pretest questions, so do your best on every part of the exam.