<P> In a scientific study, post hoc analysis (from Latin post hoc, "after this") consists of analyses that were not specified before seeing the data . This typically creates a multiple testing problem because each potential analysis is effectively a statistical test . Multiple testing procedures are sometimes used to compensate, but that is often difficult or impossible to do precisely . Post hoc analysis that is conducted and interpreted without adequate consideration of this problem is sometimes called data dredging by critics, because the more one looks the more likely something will be found . </P> <P> Sometimes the temptation to engage in post hoc analysis is motivated by a desire to produce positive results or see a project as successful . In the case of pharmaceutical research, there may be significant financial consequences to a failed trial, although the US Food and Drug Administration does not accept post hoc analysis . </P>

When do we conduct a post hoc analysis
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