Editing Sampling bias (section)

==Distinction from selection bias==
Sampling bias is usually classified as a subtype of [[selection bias]],<ref>{{cite web | url = http://medical.webends.com/kw/Selection%20Bias | work = Dictionary of Cancer Terms | title = Selection Bias | archive-url = https://web.archive.org/web/20090609002707/http://medical.webends.com/kw/Selection%20Bias | archive-date = 9 June 2009 | access-date = 23 September 2009 }}</ref> sometimes specifically termed '''sample selection bias''',<ref name="ArdsChung1998">{{cite journal | vauthors = Ards S, Chung C, Myers SL | title = The effects of sample selection bias on racial differences in child abuse reporting | journal = Child Abuse & Neglect | volume = 22 | issue = 2 | pages = 103–15 | date = February 1998 | pmid = 9504213 | doi = 10.1016/S0145-2134(97)00131-2 | doi-access = free }}</ref><ref name="CortesMohri2008">{{cite book | vauthors = Cortes C, Mohri M, Riley M, Rostamizadeh A |chapter=Sample Selection Bias Correction Theory|title=Algorithmic Learning Theory|volume=5254|year=2008|pages=38–53|chapter-url=http://www.cs.nyu.edu/~mohri/postscript/bias.pdf|doi=10.1007/978-3-540-87987-9_8|arxiv=0805.2775|series=Lecture Notes in Computer Science|isbn=978-3-540-87986-2|citeseerx=10.1.1.144.4478|s2cid=842488}}</ref><ref name="CortesMohri2014">{{cite journal | vauthors = Cortes C, Mohri M |title=Domain adaptation and sample bias correction theory and algorithm for regression|journal=Theoretical Computer Science|volume=519|year=2014|pages=103–126 |url= http://www.cs.nyu.edu/~mohri/pub/nsmooth.pdf |doi=10.1016/j.tcs.2013.09.027|citeseerx=10.1.1.367.6899}}</ref> but some classify it as a separate type of bias.<ref name="Fadem2009">{{cite book| vauthors = Fadem B |title=Behavioral Science|url=https://books.google.com/books?id=f0IDHvLiWqUC|year=2009|publisher=Lippincott Williams & Wilkins|isbn=978-0-7817-8257-9|page=262}}</ref>
A distinction, albeit not universally accepted, of sampling bias is that it undermines the [[external validity]] of a test (the ability of its results to be generalized to the entire population), while [[selection bias]] mainly addresses [[internal validity]] for differences or similarities found in the sample at hand. In this sense, errors occurring in the process of gathering the sample or cohort cause sampling bias, while errors in any process thereafter cause selection bias.

However, selection bias and sampling bias are often used synonymously.<ref name="Wallace2007">{{cite book| vauthors = Wallace R |title=Maxcy-Rosenau-Last Public Health and Preventive Medicine|url=https://books.google.com/books?id=EBq63uyt87QC |edition=15th|year=2007|publisher=McGraw Hill Professional|isbn=978-0-07-159318-2|page=21}}</ref>