An instructor should follow an established _____ when administering and scoring oral tests.

The correct answer, scoring rubric, is essential for providing a standardized method to evaluate students during oral tests. A scoring rubric outlines specific criteria and performance levels, which helps ensure that all students are assessed in a fair and objective manner. By using a scoring rubric, an instructor can clearly communicate expectations to the students and provide consistent feedback based on predetermined standards.

This approach minimizes subjectivity in grading and allows for a structured assessment of student performance. It also aids in identifying areas where individual students may need improvement, making it a valuable tool for both instructors and learners in the educational process.

In contrast, a few of the other options may not provide the systematic approach needed for scoring. For example, an answer key is typically used for multiple-choice or written tests where there are specific correct answers, but this format does not apply to oral presentations. A graph would not typically serve as an assessment tool for oral tests, and while a plan of instruction is essential for guiding the course, it does not directly pertain to the administration and scoring of tests. Therefore, the scoring rubric stands out as the most appropriate choice in this context.