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

			(1)
			(2)
			(3)

where  is the normalized correlation coefficient

(4)

For ,

(5)

The identical result is obtained for oversampling. For undersampling, the signal-to-noise ratio decreases (Thompson et al. 1986).

REFERENCES:

Feuer, A. Sampling in Digital Signal Processing and Control. Boston, MA: Birkhäuser, 1996.

Govindarajulu, Z. Elements of Sampling Theory and Methods. Upper Saddle River, NJ: Prentice-Hall, 1999.

Thompson, A. R.; Moran, J. M.; and Swenson, G. W. Jr. Interferometry and Synthesis in Radio Astronomy. New York: Wiley, pp. 214-216, 1986.