Participants have to be carefully chosen because of their expertise, experience or knowledge in the field of the research question. In addition, the variety of positions in the field or opinions regarding the subject, should be covered. In that way, lay people could be added to increase the variety of viewpoints102.
They could be identified through publically available bibliographic information102. Snowballing recruitment could be useful to secure easy agreement to panelist invitation and strengthen panelist retention102.
There is no practical limit to the number of participants in a Delphi survey89.