I don't think belief has a consistent evidentiary strength since it depends on the testifier's credibility relative to my own. Children have much lower credibility than me on the issue of the existence of Santa. Professors of physics have much higher credibility that me on the issue of dimensions greater than four. Some person other than me has much higher credibility on the issue of how much money they are carrying. But I have more credibility than anyone else on the issue of how much money I'm carrying. I don't see any relation that could be described as baseline so the only answer is: context.