Recall bias


In epidemiological research, recall bias is a systematic error caused by differences in the accuracy or completeness of the recollections retrieved by study participants regarding events or experiences from the past. Sometimes also referred to as response bias, responder bias or reporting bias, this type of measurement bias can be a methodological issue in research involving interviews or questionnaires, in which case it could lead to misclassification of various types of exposure. Recall bias is of particular concern in retrospective studies that use a case-control design to investigate the etiology of a disease or psychiatric condition. For example, in studies of risk factors for breast cancer, women who have had the disease may search their memories more thoroughly than members of the unaffected control group for possible causes of their cancer. Those in the case group may be able to recall a greater number of potential risk factors they had been exposed to than those in the control group. This can potentially exaggerate the relation between a potential risk factor and the disease. To minimize recall bias, some clinical trials have adopted a "wash out period", i.e., a substantial time period that must elapse between the subject's first observation and their subsequent observation of the same event.