Editing Selection bias (section)

===Observer selection===
Philosopher [[Nick Bostrom]] has argued that data are filtered not only by study design and measurement, but by the necessary precondition that there has to be someone doing a study. In situations where the existence of the observer or the study is correlated with the data, observation selection effects occur, and [[anthropic reasoning]] is required.<ref>{{cite book |first=Nick |last=Bostrom |title=Anthropic Bias: Observation Selection Effects in Science and Philosophy |publisher=Routledge |location=New York |year=2002 |isbn=978-0-415-93858-7 }}</ref>

An example is the past [[impact event]] record of Earth: if large impacts cause mass extinctions and ecological disruptions precluding the evolution of intelligent observers for long periods, no one will observe any evidence of large impacts in the recent past (since they would have prevented intelligent observers from evolving). Hence there is a potential bias in the impact record of Earth.<ref>{{Cite journal | doi = 10.1111/j.1539-6924.2010.01460.x| pmid = 20626690| title = Anthropic Shadow: Observation Selection Effects and Human Extinction Risks| journal = Risk Analysis| volume = 30| issue = 10| pages = 1495–506| year = 2010| last1 = Ćirković | first1 = M. M. | last2 = Sandberg | first2 = A. | last3 = Bostrom | first3 = N. | bibcode = 2010RiskA..30.1495C| s2cid = 6485564}}</ref> Astronomical [[existential risks]] might similarly be underestimated due to selection bias, and an anthropic correction has to be introduced.<ref>{{Cite journal | doi = 10.1038/438754a| title = Astrophysics: Is a doomsday catastrophe likely?| journal = Nature| volume = 438| issue = 7069| pages = 754| year = 2005| last1 = Tegmark | first1 = M. | last2 = Bostrom | first2 = N. | pmid=16341005| bibcode = 2005Natur.438..754T| s2cid = 4390013| doi-access = free}}</ref>