Editing Standard error (section)

==== Accuracy of the estimator ====
When the sample size is small, using the standard deviation of the sample instead of the true standard deviation of the population will tend to systematically underestimate the population standard deviation, and therefore also the standard error. With ''n'' = 2, the underestimate is about 25%, but for ''n'' = 6, the underestimate is only 5%. Gurland and Tripathi (1971) provide a correction and equation for this effect.<ref>{{cite journal |last=Gurland |first=J |author2=Tripathi RC | year=1971 |title=A simple approximation for unbiased estimation of the standard deviation |journal=American Statistician | volume=25 |issue=4 |pages=30–32 |doi=10.2307/2682923 |jstor=2682923 }}</ref> Sokal and Rohlf (1981) give an equation of the correction factor for small samples of ''n'' < 20.<ref>{{cite book |last1=Sokal |last2=Rohlf |year=1981 |title=Biometry: Principles and Practice of Statistics in Biological Research |edition=2nd |isbn=978-0-7167-1254-1 |page=[https://archive.org/details/biometryprincipl00soka/page/53 53] |publisher=W. H. Freeman |url-access=registration |url=https://archive.org/details/biometryprincipl00soka/page/53 }}</ref> See [[unbiased estimation of standard deviation]] for further discussion.