Membership in a specific group can be associated with a degree of health that differs significantly from the general population. Doing a study that focused specifically on joggers, or the employed, or physicians may suffer from membership bias.
Membership bias is a type of selection bias.
This post is part of a series of posts on bias in medical research. You can find the whole bias catalogue here.
You can find more evidence based medicine resources here.
References
Sackett DL. Bias in analytic research. Journal of chronic diseases. 1979; 32(1-2):51-63. PMID: 447779
Morgenstern, J. Membership bias, First10EM, April 10, 2018. Available at:
https://doi.org/10.51684/FIRS.5861