This lecture introduces sensitivity analysis in the context of life cycle assessment, focusing on the systematic procedure to estimate the effects of methodological and data choices. It covers the verification of final results by assessing the influence of variations in assumptions, methodologies, and data. The analysis distinguishes between continuous parameters, such as transport distance and energy consumption, and discontinuous parameters, like allocation rules and system boundaries. Through case studies on coffee cups, the lecture demonstrates how small changes in parameters can impact environmental outcomes. It also explores the sensitivity of results to variations in parameters, providing insights into the robustness of life cycle assessment outcomes.