To assess the efficacy and performance of an intervention or policy, impact assessment plays a crucial role. This article aims to systematically combine the existing literatures published on impact assessment methodologies using a narrative approach. Databases such as Springer, Google Scholar and Science Direct are used to identify the literature sources on different impact assessment methodologies such as Difference in Difference (DID), Propensity Score Matching, Instrumental Variable Analysis, Randomized Controlled Trial, Regression Discontinuity Design and Synthetic Control Method. Although these techniques have always been significant, their implementation varies across scientific domains due to challenges such as resource constraints and methodological complexities. To address current global issues and enhance the precision of methodologies across field, recognizing the contextual relevance of each method is essential. Each methodology offers unique characteristic uses and is characterized to solve various research issues. This helps in decision making strategies for future-oriented programs. The study emphasizes the portability and wider interdisciplinary uses of these approaches by investigating their practical application in several domains such as health, education and the environment. The limitations, challenges and intrinsic biases associated with different methodologies are analyzed and discussed. The article evaluates various approaches in assessing the impact, thereby aiding the reader to understand the appropriate methodologies for different conditions.
