I don't know what the "average" score is. It would depend on what group you are interested in. People with credit scores about 650 and above get the best interest rates. Groups in this category have a good credit record. People with a slight blemish would probably be in a 625 - 649 range. That would begin to indicate that they are a credit risk and their interest rates would be higher. They probably have one or two adverse items in their credit record.
Credit scores can run from 300 - 900, so you can see that people who score low have the most derogatory information in their records and are usually rejected for credit because they are too great of a risk.
Then too, we must figure into the equation that every company has their own set of guidelines to extending credit, so that has to be factored into the deal also. I would feel pretty confident in saying that people who have and maintain credit scores over 650 won't be denied credit, unless they are extended to the max. Those 700 and above won't have any problems getting a loan with a good interest rate.
And thank you for sharing your expertise and knowledge. The things you learn on FR, eh?