Publication Bias: The “File-Drawer” Problem in Scientific Inference

Publication bias arises whenever the probability that a study is published depends on the statistical significance of its results. This bias, often called the file-drawer effect because the unpublished results are imagined to be tucked away in researchers’ file cabinets, is a potentially severe impediment to combining the statistical results of studies collected from the literature. With almost any reasonable quantitative model for publication bias, only a small number of studies lost in the file drawer will produce a significant bias. This result contradicts the well-known fail-safe file-drawer (FSFD) method for setting limits on the potential harm of publication bias, widely used in social, medical, and psychic research. This method incorrectly treats the file drawer as unbiased and almost always misestimates the seriousness of publication bias. A large body of not only psychic research, but medical and social science studies as well, has mistakenly relied on this method to validate claimed discoveries. Statistical combination can be trusted only if it is known with certainty that all studies that have been carried out are included. Such certainty is virtually impossible to achieve in literature surveys.