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Session 2526

Teaching the Principles and Practice of Uncertainty in the Undergraduate Laboratory

Sheldon M. Jeter

Georgia Institute of Technology

INTRODUCTION

Uncertainty is the estimate of the confidence interval for a measurement. Some reasonable estimate of the uncertainty is almost always necessary. For one example, an estimate of the uncertainty is necessary to assess the reliability of measured data for use in design or analysis. An uncertainty estimate is also needed to evaluate the confidence interval when the measured value is to be compared with another measurement or with an empirical or theoretical model. Indeed, an idea of at least the order of magnitude of the uncertainty is needed merely to identify the least significant digit in the measurement so that the proper number of significant digits can be reported.

Clearly, undergraduate engineering students need instruction and practice with uncertainty. This need may be accentuated in the current curriculum because this topic may on longer be given as much or as consistent emphasis as was prevalent in traditional undergraduate science courses. This paper describes the general presentation of instruction on uncertainty in an undergraduate laboratory sequence at Georgia Tech with particular attention to several experiments that emphasize the principles of uncertainly.

The terminology and principles adopted in the mechanical engineering undergraduate laboratory sequence are based on the concepts adopted by the ISO (1995). A consistent presentation of these ideas is also available in a technical note by Taylor and Kuyatt (1994). The note also includes helpful explanations and examples. The latter report is available online in full and summary versions. Both online versions are excellent and handy resources for students. This paper and the presentation to students described herein do not pretend to present any new concepts. Instead the goal of this paper is to describe one approach to teaching the concepts of uncertainty. Some empirical examples to reinforce the ideas are also presented. Overall this paper describes an approach to education about uncertainty that attempts to be systematic and consistent with the pertinent publications and general understanding.

One of the salient features of the new approach to uncertainty is the use of the unified and clearly defined term uncertainty itself. In the past, the terms accuracy and precision were usually employed. Accuracy referred to the closeness to the presumed true value, and precision referred to the repeatability of measurements. These commonplace terms were easily confused. Introducing a word that is fresher in this context along with explicit original definitions for its use is a great improvement in clarity. Another advantage is semantic. It is easily confusing to say “increasing the accuracy” when it is meant that the confidence interval is decreased. In contrast, saying that the “uncertainty is increased” is consistent with increasing the confidence interval.

Proceedings of the 2001 American Society for Engineering Education Annual Conference & Exposition Copyright  2001, American Society for Engineering Education

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Jeter, S. (2001, June), Teaching The Principles And Practice Of Uncertainty In The Undergraduate Laboratory Paper presented at 2001 Annual Conference, Albuquerque, New Mexico. 10.18260/1-2--9879