Common Source Bias
Common source bias refers to biases or inaccuracies that can occur when combining or comparing research studies, especially when those studies come from the same source, or from sources that use the same methodologies. When unrecognized, this type of bias can seriously effect the truth and accuracy of the findings derived from those studies.
This type of bias, on its simplest level, can derive from the content of specific items, scale type, response format, and the general context of the study. For instance, in comparing two rat maze studies it would be necessary to compare the methods used; Was the same type of maze used? Was the same reward or punishment used? Were the results measured the same way? The researches need to ask these questions to determine whether the studies are comparable.