This e-book presents state-of-the-art research in the field of quantitative approaches and modeling in marketing. A wide range of topics are covered, including (i) analytical and empirical models of international airline demand forecasting with discussion on managerial and public policy implications, (ii) analysis of endogeneity problems in demand models and recommendation of procedures for managing this problem, (iii) a dynamic exchange model between firm and salesperson as well as transaction cost economics theory to explore the conditions affecting salesperson profitability in a relationship perspective, and providing managerial actions on how to motivate salespeople to invest time and effort in developing skills and relationships with customers, and (iv) examination of several tests available in the statistical literature to assess normality of a given set of data, and making specific suggestions for testing for normality before data analysis.