A sample is a group selected from a population. Inferences about a population can be made from information
obtained in a sample when the sample is representative of the population. Samples based on planned randomness
are called probability samples. Probability sampling has a certain amount of randomness built in so that bias or
unbiasedness can be established and probability statements could be made about the accuracy of the methods
(Scheaffer, Mendenhall, & Ott, 1996). Randomization inherent in probability sampling helps balance out variables that
cannot be controlled or measured directly.