The impact of negative marking on the UPSC preliminary examination is significant, as it discourages random guessing. This marking scheme penalizes incorrect answers, prompting candidates to be more judicious in their choices. It emphasizes the need for a well-thought-out strategy rather than relying on luck, encouraging a deeper understanding of the syllabus. Candidates must be well-prepared, as the pressure of potential negative marks can influence decision-making during the exam. Overall, negative marking aims to uphold the integrity and quality of the examination, ensuring that only those with a solid grasp of the material progress.