Changes

==Selection bias==

==Selection bias==

Selection bias results in the selection of a study sample which is not representative of the source population, and so affects inclusion of individuals in the study.

Selection bias affects inclusion of individuals in the study and results in the study sample not being representative of the source population. This may occur in the initial selection process, or may be a result of nonresponse or losses to follow up during the study period. The mechanisms by which selection bias can enter a study will depend on the study design:

 

 

==Information bias==

==Information bias==