Measurements and Uncertainty

This chapter describes the importance of the measurement process. The ability to improve the quality of data extracted in a particular situation depends strongly on an understanding of the concepts of precision and uncertainty. Every measurement has three components: the number itself, the units, and the uncertainty associated with the number. The chapter discusses briefly the units and the number reported, and explains how to estimate uncertainty, how to work with uncertainty, and how to report uncertainty. In the context of science and engineering, error generally means an experimental uncertainty. It is common to separate errors into three types: systematic errors, random errors, and illegitimate errors. The chapter provides a simplified introduction to probability and the propagation of uncertainties, and then describes the standard deviation formulas. It describes general methods, namely direct or brute‐force method, that can be used to determine how component errors affect the final value.