Fred,
Lawrence and Ellie gave you the name of the documents that would indicate the ratio for FHA guidelines. Here is a link to a
thread that had links to the document in it. No bank will release what is or isn't the deciding factor in making a loan. The FHA issues guidelines on what they will require if they were to purchase the note from the bank. Because Franny and Freddie are the main purchaser of the notes, most banks will include those requirements within their own approval criteria. However, those guidelines are not necessarily absolutes for the bank in making their decision.
Unless someone has other information, I believe that what Lawrence and Ellie provided will probably be the only written documentation you will be able to get.
Tim