Selective reporting is the reporting of results from only a selection of studies. Selective reporting can lead to publication bias. For example, if a greater proportion of studies with a positive outcome are reported than those with a negative outcome, a review of publications will be biased toward a positive result.
Selective reporting can arise if, for example, an investigator, journal editor, or trial sponsor thinks that negative results (where no effect of a new medicine is found) are uninteresting or unimportant. However, the reporting of negative results adds valuable information to the body of evidence available, and can prevent new unnecessary trials being set up.