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第292行： − + − + − Where E[ ] stands for expectation taken over the error terms.+ − 其中 e []表示期望取代了错误项。+ − − While the concept of mediation as defined within psychology is theoretically appealing, the methods used to study mediation empirically have been challenged by statisticians and epidemiologists<ref name="Robins">{{cite journal | last1 = Robins | first1 = J. M. | author-link = James Robins | author-link2 = Sander Greenland | last2 = Greenland | first2 = S. | year = 1992 | title = Identifiability and exchangeability for direct and indirect effects | journal = Epidemiology | volume = 3 | issue = 2| pages = 143–55 | doi = 10.1097/00001648-199203000-00013 | pmid = 1576220 }}</ref><ref name="Kaufman">{{cite journal|pmc=526390|doi=10.1186/1742-5573-1-4|year=2004|last1=Kaufman|first1=J. S.|title=A further critique of the analytic strategy of adjusting for covariates to identify biologic mediation|journal=Epidemiologic Perspectives & Innovations |volume=1|issue=1|pages=4|last2=MacLehose|first2=R. F.|last3=Kaufman|first3=S|pmid=15507130}}</ref><ref name="Bullock">{{cite journal|pmid=20307128|url=http://www2.psych.ubc.ca/~schaller/528Readings/BullockGreenHa2010.pdf|year=2010|last1=Bullock|first1=J. G.|title=Yes, but what's the mechanism? (don't expect an easy answer)|journal=Journal of Personality and Social Psychology|volume=98|issue=4|pages=550–8|last2=Green|first2=D. P.|last3=Ha|first3=S. E.|doi=10.1037/a0018933}} − − </ref> and interpreted formally.<ref name="Pearl-01">[[Judea Pearl|Pearl, J.]] (2001) [http://ftp.cs.ucla.edu/pub/stat_ser/R273-U.pdf "Direct and indirect effects"]. Proceedings of the Seventeenth Conference on Uncertainty in Artificial Intelligence, [[Morgan Kaufmann]], 411–420.</ref> − These effects have the following interpretations:+ − 这些影响有以下解释:+ +
→Approaches to mediation
==Approaches to mediation==
==Approaches to mediation==
<math> NIE = E [Y(0,M(1)) - Y(0,M(0))] </math>
While the concept of mediation as defined within psychology is theoretically appealing, the methods used to study mediation empirically have been challenged by statisticians and epidemiologists<ref name="Robins">{{cite journal | last1 = Robins | first1 = J. M. | author-link = James Robins | author-link2 = Sander Greenland | last2 = Greenland | first2 = S. | year = 1992 | title = Identifiability and exchangeability for direct and indirect effects | journal = Epidemiology | volume = 3 | issue = 2| pages = 143–55 | doi = 10.1097/00001648-199203000-00013 | pmid = 1576220 }}</ref><ref name="Kaufman">{{cite journal|pmc=526390|doi=10.1186/1742-5573-1-4|year=2004|last1=Kaufman|first1=J. S.|title=A further critique of the analytic strategy of adjusting for covariates to identify biologic mediation|journal=Epidemiologic Perspectives & Innovations |volume=1|issue=1|pages=4|last2=MacLehose|first2=R. F.|last3=Kaufman|first3=S|pmid=15507130}}</ref><ref name="Bullock">{{cite journal|pmid=20307128|url=http://www2.psych.ubc.ca/~schaller/528Readings/BullockGreenHa2010.pdf|year=2010|last1=Bullock|first1=J. G.|title=Yes, but what's the mechanism? (don't expect an easy answer)|journal=Journal of Personality and Social Psychology|volume=98|issue=4|pages=550–8|last2=Green|first2=D. P.|last3=Ha|first3=S. E.|doi=10.1037/a0018933}}
</ref> and interpreted formally.<ref name="Pearl-01">[[Judea Pearl|Pearl, J.]] (2001) [http://ftp.cs.ucla.edu/pub/stat_ser/R273-U.pdf "Direct and indirect effects"]. Proceedings of the Seventeenth Conference on Uncertainty in Artificial Intelligence, [[Morgan Kaufmann]], 411–420.</ref>
(1) Experimental-causal-chain design
An experimental-causal-chain design is used when the proposed mediator is experimentally manipulated. Such a design implies that one manipulates some controlled third variable that they have reason to believe could be the underlying mechanism of a given relationship.
(2) Measurement-of-mediation design
A measurement-of-mediation design can be conceptualized as a statistical approach. Such a design implies that one measures the proposed intervening variable and then uses statistical analyses to establish mediation. This approach does not involve manipulation of the hypothesized mediating variable, but only involves measurement.<ref>{{cite journal|pmid=16393019|url=http://www2.psych.ubc.ca/~schaller/528Readings/SpencerZannaFong2005.pdf|year=2005|last1=Spencer|first1=S. J.|title=Establishing a causal chain: Why experiments are often more effective than mediational analyses in examining psychological processes|journal=Journal of Personality and Social Psychology|volume=89|issue=6|pages=845–51|last2=Zanna|first2=M. P.|last3=Fong|first3=G. T.|doi=10.1037/0022-3514.89.6.845}}
</ref>