The assumption is that the sample is representative of the entire population. Small-business owners use sampling when determining new market niches, products and satisfaction levels.

Central Limit Theorem, or CLT, is a statistical theory stating that as the size of a sample grows, the results tend to approximate a normal distribution of results. Read more here.

Michael E. Tarter, Mean Integrated Squared Error Sampling, Journal of the American Statistical Association, Vol. 81, No. 393 (Mar., 1986), pp. 234-242 ...

This clarifies and extends standard results in sampling theory for the estimation of the mean and variance of a population. The American Statistician strives to publish articles of general interest to ...