Editing Hawthorne effect (section)

==Trial effect==
Various medical scientists have studied possible trial effect (clinical trial effect) in [[clinical trial]]s.<ref name="pone_0021824">{{Citation
 |vauthors=Menezes P, Miller WC, Wohl DA, Adimora AA, Leone PA, Eron JJ
 |year=2011
 |title=Does HAART efficacy translate to effectiveness? Evidence for a trial effect
 |journal=[[PLoS ONE]]
 |volume=6
 |issue=7
 |page=e21824
 |doi=10.1371/journal.pone.0021824
 |pmid=21765918
 |pmc=3135599
 |postscript=.
 |bibcode=2011PLoSO...621824M
 |doi-access=free
 }}</ref><ref name="pmid_11223318">{{Citation
 |vauthors=Braunholtz DA, Edwards SJ, Lilford RJ
 |year=2001
 |title=Are randomized clinical trials good for us (in the short term)? Evidence for a "trial effect"
 |journal=J Clin Epidemiol
 |volume=54
 |issue=3
 |pages=217–224
 |pmid=11223318
 |postscript=.
 |doi=10.1016/s0895-4356(00)00305-x
 }}</ref><ref name="BMC_1471-2288">{{Citation
 |vauthors=McCarney R, Warner J, Iliffe S, van Haselen R, Griffin M, Fisher P
 |year=2007
 |title=The Hawthorne Effect: a randomised, controlled trial
 |journal=BMC Medical Research Methodology
 |volume=7
 |page=30
 |doi=10.1186/1471-2288-7-30
 |postscript=.
 |pmid=17608932
 |pmc=1936999
 |doi-access=free
 }}</ref> Some postulate that, beyond just attention and observation, there may be other factors involved, such as slightly better care; slightly better [[compliance (medicine)|compliance/adherence]]; and [[selection bias]]. The latter may have several mechanisms: (1) Physicians may tend to recruit patients who seem to have better adherence potential and lesser likelihood of future [[lost to follow-up|loss to follow-up]]. (2) The inclusion/exclusion criteria of trials often exclude at least some [[comorbidity|comorbidities]]; although this is often necessary to prevent [[confounding]], it also means that trials may tend to work with healthier patient subpopulations.