This is from Psychological Science 22(11), p.1363:
- If an analysis includes a covariate, authors must report the statistical results of the analysis without the covariate. Reporting covariate-free results makes transparent the extent to which a finding is reliant on the presence of a covariate, puts appropriate pressure on authors to justify the use of the covariate, and encourages reviewers to consider whether including it is warranted. Some findings may be persuasive even if covariates are required for their detection, but one should place greater scrutiny on results that do hinge on covariates despite random assignment.
I don't understand this. Does this mean redoing the statistics after discovering a covariate and excluding that variable (What is the point?)? Or declaring ex ante what is the expected covariate?