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Unformatted text preview: I Roles of Probability and Statistics in Engineering 11 INTRODUCTION In dealing with real world problems, uncertainties are unavoidable. As engineers, it is im portant that we recognize the presence of all major sources of uncertainty in engineering. The sources of uncertainty may be classified into two broad types: (1) those that are asso ciated with natural randomness; and (2) those that are associated with inaccuracies in our prediction and estimation of reality. The former may be called the aleatory type, whereas the latter the e p i s t e l n i c t y p e . Irrespective of the type of uncertainty, probability and statistics provide the proper tool for its modeling and analysis. In the ensuing chapters we will present the fundamental principles of probability and statistics, and illustrate their applications in engineeringtype problems. The main aim of this work is to present the concepts and m eth ods of probability and statistics for the modeling and formulation of engineering problems under uncertainty: this is in contrast to hooks that are devoted to statistical data analysis. although the fundamentals of statistics are also presented here. The effects of uncertainties on the design and planning of an engineering system are important. to be sure; however, the quantification of such uncertainty and the evaluation of its effects on the performance and design of the system, should properly include the concepts and methods of probability and statistics. Furthermore, under conditions of uncertainty, the design and planning of engineering systems involve risks, which involves probability and associated consequences. and the formulation of related decisions may be based on quantitative riskbenefit tradeoffs which are properly also within the province of applied probability and statistics. In this light, and with reference to problems containing randomness and uncertainty, the significance of the concepts of probability and statistics in engineering parallels those of the principles of physics, chemistry, and mechanics in the formula tion and solution of engineering problems. In light of the above, we see that the role of probability and statistics is quite pervasive in engineering: it ranges from the description of basic information to the development and formulation of bases for design and decision making. Specific examples of such imperfect information, and of applications in engineerin g design and decisionmaking problems. are described in the following sections. 1 2 Chapter 1. Roles of Probability and Statistics in Engineering 1.2 Uncertainty in Engineering 3 1.2 UNCERTAINTY IN ENGINEERING be combined and analyzed as a total uncertainty, or treate d separately. In either case, the principles of probability and statistics apply equally. We might point out that there are good reasons to view the significance of the two types of uncertainty, and their respective effects on engineering. differently. First of all, the aleatory (databased) uncertainty...
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