Standard Error
The standard deviation of the sampling distribution of the statistic is referred to as the standard error of that quantity. For the case where the statistic is the sample mean, and samples are uncorrelated, the standard error is:
where is the standard deviation of the population distribution of that quantity and n is the size (number of items) in the sample.
An important implication of this formula is that the sample size must be quadrupled (multiplied by 4) to achieve half (1/2) the measurement error. When designing statistical studies where cost is a factor, this may have a role in understanding cost-benefit tradeoffs.
Read more about this topic: Sampling Distribution
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