This book unifies econometric theory, estimation, and interpretation into a coherent workflow for turning economic questions into testable, evidence-based claims. It develops linear regression from simple to multiple models, establishing OLS, Gauss–Markov conditions, finite-sample t/F tests, and asymptotic reasoning. Readers learn to detect and correct violations—heteroskedasticity, serial correlation, multicollinearity, functional misspecification—using robust, clustered, and HAC variance estimators with specification diagnostics. Worked examples, data-driven case studies. Aimed at advanced undergraduates, master’s and PhD students, and policy/industry practitioners, it equips readers to deliver credible, policy-relevant empirical analyses