Selection bias is a type of bias created when the data sampled is not representative of the data of the population or group that a study or model aims to make a prediction about. Selection bias is the result of systematic errors in data selection and collection. Practically-speaking selection bias often occurs when the sample size of data is incorrect or the assignment of patients or data to groups is non-random. There are many types of selection bias described in the medical literature, for example survival bias and survivorship bias which can have overlapping definitions.
Selection bias is of particular concern in terms of the development of artificial intelligence technologies . In terms of machine learning, training data to create an algorithm (as opposed to the sampled data in a study) may have a different distribution of pathology than the population for which the algorithm is intended.