Publication bias: the file drawer problem thumb|right|A funnel plot expected without the file drawer problem. The largest studies converge at the tip while smaller studies show more or less symmetrical scatter at the base. thumb|right|A funnel plot expected with the file drawer problem. The largest studies still cluster around the tip, but the bias against publishing negative studies has caused the smaller studies as a whole to have an unjustifiably favorable result to the hypothesis. Another potential pitfall is the reliance on the available body of published studies, which may create exaggerated outcomes due to publication bias, as studies which show negative results or insignificant results are less likely to be published. For example, pharmaceutical companies have been known to hide negative studies and researchers may have overlooked unpublished studies such as dissertation studies or conference abstracts that did not reach publication. This is not easily solved, as one cannot know how many studies have gone unreported.
publication bias the file drawer problem thumb|right|a funnel plot expected without the file drawer problem the largest studies converge at the tip while smaller studies show more or less symmetrical scatter at the base thumb|right|a funnel plot expected with the file drawer problem the largest studies still cluster around the tip but the bias against publishing negative studies has caused the smaller studies as a whole to have an unjustifiably favorable result to the hypothesis another potential pitfall is the reliance on the available body of published studies which may create exaggerated outcomes due to publication bias as studies which show negative results or insignificant results are less likely to be published for example pharmaceutical companies have been known to hide negative studies and researchers may have overlooked unpublished studies such as dissertation studies or conference abstracts that did not reach publication this is not easily solved as one cannot know how many studies have gone unreported