What is the purpose of a mark scheme in exam evaluation?

The purpose of a mark scheme in exam evaluation is to provide guidelines for evaluating exam responses consistently. A mark scheme outlines the criteria that examiners will use to assess students' answers, ensuring that grading is fair and impartial across different responses and examiners. By having clear guidelines, it enables educators to maintain a standard in the evaluation process, leading to reliable and valid assessment outcomes.

In contrast, the other options touch on different aspects of the educational and evaluation process. Defining the curriculum relates to what content is taught and assessed but does not directly involve the evaluation of responses. Determining the subject matter of the exam is related to the planning and preparation phase rather than the evaluation itself. Calculating overall student grades is a broader administrative action that occurs after evaluations are made, not the specific function of a mark scheme. Thus, the emphasis on consistent evaluation as guided by the mark scheme is what makes it essential for fair and effective assessment practices.