To improve the quality and credibility of your economic impact assessment, you can use a combination of quantitative and qualitative methods, a framework or model, benchmarks and comparisons, sensitivity and scenario analysis, and peer review and feedback. For example, if you want to measure the economic impact of a new online learning platform, you could define the scope and objectives of your analysis, choose the appropriate indicators and metrics, collect and analyze the data, and report and communicate the results. You could use data sources such as the platform's records and analytics, surveys and interviews with learners and instructors, external databases and reports, academic and industry studies, statistical models, and simulation techniques. Furthermore, you could present your findings in a clear way using tables, charts, graphs, infographics, etc., while highlighting key messages and insights. It's important to also acknowledge the limitations of your analysis as well as provide sources for your data.