Managerial economics uses both Economic theory as well as Econometrics for rational managerial decision making. Econometrics is defined as use of statistical tools for assessing economic theories by empirically measuring relationship between economic variables. It uses factual data for solution of economic problems. Managerial Economics is associated with the economic theory which constitutes Theory of Firm. Theory of firm states that the primary aim of the firm is to maximize wealth. Decision making in managerial economics generally involves establishment of firms objectives, identification of problems involved in achievement of those objectives, development of various alternative solutions, selection of best alternative and finally implementation of the decision.
Managerial economics is the "application of the economic concepts and economic analysis to the problems of formulating rational managerial decisions".  It is sometimes referred to as business economics and is a branch of economics that applies microeconomic analysis to decision methods of businesses or other management units. As such, it bridges economic theory and economics in practice.  It draws heavily from quantitative techniques such as regression analysis , correlation and calculus .  If there is a unifying theme that runs through most of managerial economics, it is the attempt to optimize business decisions given the firm's objectives and given constraints imposed by scarcity, for example through the use of operations research , mathematical programming , game theory for strategic decisions,  and other computational methods .