Case-control studies are particularly susceptible to selection bias. A major source of selection bias in these studies is through the selection of the '''control group'''. As mentioned above, it is of vital importance that the control group comes from the same population as the case group (that is, if they happened to experience the outcome of interest during the study period, they would have been classified as a case instead of a control). ''Admission risk bias'' is a type of selection bias associated with hospital-based studies where cases and controls are selected from hospitals (or similar establishments), and so may have a different exposure profile to the general population (to which the results are generally intended to be extrapolated). However, selection of controls from other sources can also introduce biases. Detection bias is a form of selection bias which results from differential classification of disease status according to exposure status (and so is closely related to '''information bias'''). | Case-control studies are particularly susceptible to selection bias. A major source of selection bias in these studies is through the selection of the '''control group'''. As mentioned above, it is of vital importance that the control group comes from the same population as the case group (that is, if they happened to experience the outcome of interest during the study period, they would have been classified as a case instead of a control). ''Admission risk bias'' is a type of selection bias associated with hospital-based studies where cases and controls are selected from hospitals (or similar establishments), and so may have a different exposure profile to the general population (to which the results are generally intended to be extrapolated). However, selection of controls from other sources can also introduce biases. Detection bias is a form of selection bias which results from differential classification of disease status according to exposure status (and so is closely related to '''information bias'''). |