Research_Design_And_Methodological_Principle encompasses the fundamental frameworks, guidelines, and logical structures that underpin rigorous sociological inquiry. This category includes the foundational elements of scientific research design, from hypothesis formulation and operational definition of concepts to the establishment of causal relationships through systematic investigation. The scientific method provides the overarching framework for conducting objective, replicable research, while research principles ensure ethical conduct and methodological rigor. Applied social research connects academic inquiry to practical problem-solving, emphasizing the translation of findings into actionable solutions for social issues. Causal logic and causation represent critical analytical concepts for understanding relationships between variables and establishing explanatory frameworks. These principles guide researchers in developing coherent research strategies, selecting appropriate methods, and maintaining standards of validity and reliability. The category emphasises the importance of systematic planning, logical reasoning, and methodological transparency in producing credible knowledge that can advance sociological theory and inform evidence-based practice in addressing complex social challenges.