Editing Standard deviation (section)

===Bounds on standard deviation===
For a set of {{math|{{var|N}} > 4}} data spanning a range of values {{mvar|R}}, an upper bound on the standard deviation {{mvar|s}} is given by {{math|{{var|s}} {{=}} 0.6{{var|R}}}}.<ref>{{Cite journal | doi=10.1111/j.1467-9639.1980.tb00398.x| title=Upper and Lower Bounds for the Sample Standard Deviation| journal=Teaching Statistics| volume=2| issue=3| pages=84–86| year=1980| last1=Shiffler| first1=Ronald E.| last2=Harsha| first2=Phillip D.}}</ref> 
An estimate of the standard deviation for {{math|{{var|N}} > 100}} data taken to be approximately normal follows from the heuristic that 95% of the area under the normal curve lies roughly two standard deviations to either side of the mean, so that, with 95% probability the total range of values {{mvar|R}} represents four standard deviations so that {{math|{{var|s}} ≈ {{var|R}}/4}}. This so-called range rule is useful in [[sample size]] estimation, as the range of possible values is easier to estimate than the standard deviation. Other divisors {{math|{{var|K}}({{var|N}})}} of the range such that {{math|{{var|s}} ≈ {{var|R}}/{{var|K}}({{var|N}})}} are available for other values of {{mvar|N}} and for non-normal distributions.<ref>{{Cite journal |jstor = 2685690|title = Using the Sample Range as a Basis for Calculating Sample Size in Power Calculations|journal = The American Statistician|volume = 55|issue = 4|pages = 293–298|last1 = Browne|first1 = Richard H.|year = 2001|doi = 10.1198/000313001753272420|s2cid = 122328846}}</ref>