Difference between revisions of "Random sampling"
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| − | '''Random sampling''' is a [[statistical]] technique which gives everyone in the target group the same opportunity to participate in a [[poll]]. | + | '''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. |
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| + | 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. | 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. | ||
Revision as of 14:27, February 28, 2009
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.
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.