A simple random sample of size 
from a finite population of
size 
is a sample selected so that each of the 
subsets of size 
has the same probability of
being selected. Equivalently, sampling units are chosen without replacement by a
uniform random mechanism.
Simple Random Sample
See also
Cluster Sampling, Population, Sample, Sampling, Stratified SamplingExplore with Wolfram|Alpha
References
Cochran, W. G. Sampling Techniques, 3rd ed. New York: Wiley, 1977.Cite this as:
Weisstein, Eric W. "Simple Random Sample." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/SimpleRandomSample.html