Metrology is a science that uses some statistical concepts, especially for the declaration of measurement uncertainty. Before we present these statistical tools, it is essential to discuss initially the idea of significant digits, although there is no direct correlation between the subjects. The reason is that in this chapter, we highlight only the statistics applied to metrology, that is, to deal with the analysis of data obtained from measurements, and, thus, the results of these statistics should be compatible with the number of significant digits of the original measurements. In declaring the reading resolution of the measuring instruments, the uncertainties, and the measurement’s result, we must consider the correct number of significant digits. A normative document recommends declaring measurement uncertainty with a maximum of two significant digits.