ABOUT PEW RESEARCH CENTER Pew Research Center is a nonpartisan, nonadvocacy fact tank that informs the public about the issues, attitudes and trends shaping the world. It does not take policy ...

Nature PortfolioOn this page Journal specific instructions Nature journal pledge to authors How to publish your research in a Nature journal Editorial Process About advance online publication ...

Course TopicsPower analyses and sample size calculations are important parts of many research projects. Often, before data are even collected, it is necessary to calculate and justify the required ...