In statistics, sampling is the selection and implementation of statistical observations in order to estimate properties of an underlying population. Sampling is a vital
part of modern polling, market research, and manufacturing, and its proper use is
vital in the functioning of modern economies. The portion of a population
selected for analysis is known as a sample, and the number
of members in the sample is called the sample size.

The term "sampling" is also used in signal processing to refer to measurement of a signal at discrete times, usually with the intension of reconstructing the original
signal. For infinite-precision sampling of a band-limited signal at the Nyquist
frequency, the signal-to-noise ratio
after samples is