A study compared two groups (differing on factor A) on ability X and found that X differs between the two groups (effect of A). However, the groups also differ on a not interesting variable B (say, "age"). When using B as covariate in the analysis of A on X, there is no effect of A.
In the statistical analysis (ANCOVA) the authors present the statistics for X corrected for B (i.e. "no significant effect of A on X"), however, next to this analysis, they present the effect sizes (Cohen's d) of the raw/uncorrected values of X as support for their hypothesis ("large effect of A on X"). They do not attempt to make it obvious that these effect sizes are based on scores without correcting for B.
I think they have to present the effect sizes of A corrected for B (i.e. after regressing out the effect of B on X). However, they don't want to, possibly because they have a strong hypothesis about A affecting X.
Is what they are doing correct, is it normal, is it misleading or even fraud?