Random sampling

Random sampling is a statistical technique which gives everyone in the target group the same opportunity to participate in a poll. Moree exactly, everyone has a known probability of selectionb. This ensures the validity of the poll, meaning that the results reflect the target population.

The reliability of a poll is a different dimension and refers to the amount of random error still present. The larger the poll, the smaller the random error. (Increasing the size of a poll by X reduces the error by the square root of x. A poll with 4 times as many people will have half the random error.)

An example is all eligible voters being equally likely to be included in a poll. This method does not ensure accuracy, but increases its likelihood.

Theory

In statistical studies, random sampling refers to the extraction of values (sampling) of a designated input probability distribution for ensuing statistical calculations, such that the relative probability of extraction is that indicated by the input probability density function in the case of a continuous distribution or the probability mass function in the case of a discrete distribution.

Further reading

• Graham Kalton. Introduction to Survey Sampling (Quantitative Applications in the Social Sciences) (1983) [http://www.amazon.com/Introduction-Sampling-Quantitative-Applications-Sciences/dp/0803921268/ref=sr_1_2?ie=UTF8&s=books&qid=1235831356&sr=1-2 excerpt and text search[

[Category:Statistics]]