The authors pointed out that credibility is a perception. It can be usefully evaluated as having two qualities, trustworthiness and expertise.
Trustworthiness, a key element of the credibility calculus, is defined by the terms well-intentioned, truthful, unbiased, and so on. The trustworthiness dimension of credibility captures the perceived goodness or morality of the source.
Expertise, the other dimension of credibility, is defined by terms such as knowledgeable, experienced, competent, and so on. The expertise dimension of credibility captures the perceived knowledge and skill of the source.[2]