_:vb50935006 . _:vb50935007 . _:vb50935009 _:vb50935010 . _:vb50935011 . . _:vb50935009 . _:vb50935007 _:vb50935008 . "observational study draws inferences about the possible effect of a treatment on subjects, where the assignment of subjects into a treated group versus a control group is outside the control of the investigator"@en . _:vb50935010 ":arcc045b454" . _:vb50935011 ":arcc045b453" . _:vb50935011 . . _:vb50935007 ":arcc045b450" . "observational study"@en . _:vb50935010 _:vb50935011 . _:vb50935008 _:vb50935009 . . _:vb50935011 . _:vb50935011 . _:vb50935008 ":arcc045b451" . _:vb50935006 . _:vb50935007 . _:vb50935008 . _:vb50935006 . _:vb50935008 . _:vb50935006 ":arcc045b449" . . _:vb50935006 . _:vb50935007 . _:vb50935009 . _:vb50935010 . _:vb50935007 . _:vb50935009 ":arcc045b452" . "SIO_000976" . _:vb50935010 . _:vb50935006 .