Bias: a pitfall for the validity of a study

Abstract

A bias is one of the major concerns in almost all types of epidemiological studies. It is defined as any systematic error in the design, conduct, or analysis of a study that causes an incorrect estimate of an exposure’s effect on the risk of illness. There are several types of bias that can be classified in two main groups: selection bias and information bias. In a selection bias the error is introduced when the study population does not represent the target population. An information bias occurs when an error is introduced during the detection of exposures and/or effects, thus producing a misclassification of exposed/diseased subjects. (Epidemiology_statistics)