Selection Bias

{
  "id": "MLC-T-ENV-025146",
  "term": "Selection Bias",
  "field": "Environment",
  "definition": "1. Potential biases introduced into a study by the selection of different types of people into treatment and comparison groups. As a result, the outcome differences may potentially be explained as a result of pre-existing differences between the groups, as opposed to the treatment itself.\n\n2. An error in choosing the individuals or groups to take part in a study. Ideally, the subjects in a study should be very similar to one another and to the larger population from which they are drawn (for example, all individuals with the same disease or condition). If there are important differences, the results of the study may not be valid.\n\n3. Systematic difference in the enrollment of participants in a study that leads to an incorrect result (e.g., risk ratio or odds ratio) or inference.",
  "subject": "Policy and guidance",
  "references": [
    "Program Evaluation Glossary",
    "National Cancer Institute Glossary",
    "CDC Glossary: Principles of Epidemiology in Public Health Practice at https://www.cdc.gov/csels/dsepd/ss1978/SS1978.pdf"
  ],
  "url": "https://mlchart.com/terminology/environment/selection-bias/"
}