Gini's mean difference is also a robust estimator of the standard deviation .It is computed as If the observations are from a normal distribution, then is an unbiased estimator of the standard ...

Standard Error: the standard deviation of the sampling distribution. Unbiased Estimator: Statistic ω is an unbiased estimator of parameter Ω if E(ω) = Ω. If you draw many samples from a population, ...