Econometrics (measuring economy) is a basic branch of modern economics. The quantification of the economy requires an adapted approach, based on the analysis of a data set. With statistical methods, we can study the observed variables of our economy and obtain the economic relationships hold by objects and agents. The quantitative analysis of economic phenomena is based on economic theory, which must be translated into mathematical and statistical expressions. In this book we make use of the Multiple Linear Regression, a basic tool for an introductory course in Econometrics. We introduce students to the use of data sets and the multiple linear regressions, with a specifi c analysis on applications and derived problems. The book includes practical workshops to master the different techniques in several lessons.