The standard deviation of an estimator of a population parameter. The standard error of the sample mean, from a sample of size n, is , where σ2 is the population variance.
Statistics
The square root of the variance of a statistic. For example, the standard error of the sample mean of n observations taken from a population with variance σ2 is σ/√n. The term is also used for s/√n where s2 is the sample variance. The term ‘standard error’ was used by Yule in 1897.
Chemical Engineering
The estimated standard deviation of a parameter whose value is not known exactly.