Credible sources are ones the reader can trust. We trust that the author’s ideas are his or her own and can be backed up with evidence.
When writing a research paper, doing research, or reading for background information, writers should ALWAYS use a credible source. Citing noncredible sources can damage a writer’s relationship with his or her readers.
Keep in mind that the definition of a credible source depends on the audience, the topic, and the discipline.
from University Writing Center @ Appalachian State University
For example: an article from USA Today newspaper or Time magazine is credible, but it is not scholarly.