I know that interest rate change every day possibly every hour.
Currently for FHA 30 yr fixed can someone break down interests as they relate to FICO scores. I'm assuming most lenders use the middle score approach?
Middle Score Interest Rate (APR)
550 8% (i made that up)
600 6% ...........................
The Google mortgage advisor seems to be a decent tool for looking at rates available based on various parameters (down pmt, discount points, credit score). Also, you could try looking at the top of any of your recently purchased MyFico reports. Every one I've ever pulled has a table that looks just like yours. It's in the 'How Lenders See You' section.
The mortgage rate estimates that myfico.com gives you aren't very accurate, so I would disregard them. Not many lenders do 550 credit scores, so the interest rate for a 550 would be quite a bit higher than a 600 perhaps by 1/2%. You may find my response in this thread helpful.