The standard error of a
statistic is the standard
deviation of the sampling
distribution of that statistic. Standard errors are
important because they reflect how much
sampling fluctuation a statistic
will show. The inferential
statistics involved in the construction of
confidence intervals and
significance testing are based on
standard errors. The standard error of a statistic depends
on the sample size. In general, the larger the sample size
the smaller the standard error. The standard error of a
statistic is usually designated by the Greek letter sigma
(σ) with a subscript indicating
the statistic. For instance, the standard error of the
mean is indicated by the symbol:
σM.