The Standard Error is the
deviation of the mean of a
sample. If you:
- take a large number of samples, of
equal size, from a population
- calculate the mean of each sample
- calculate the standard deviation of
the sample means
you will have found the standard error.
The standard error is related to the population
(process) standard deviation by:
where 'n' is the sample size.
The standard error is less than the population
standard deviation because taking the mean
of a sample has an 'averaging' effect; the
larger and smaller values in the sample
tend to average out.