I’d find this hard to believe
***What part do you find it hard to believe? That they are designed to shoot down 10:1? F-15s were designed to shoot down 6:1 and they have a 300:0 kill ratio AFAIK. Of course, they were never presented with the scenario of overwhelming numbers coming over the borders at 7:1 or 5:1 or whatever the soviets had at the time. So these guys proceeded with the numbers they had.
10:1 against what? I depends on what you go up against and like any statistic you choose the one you want.
From an USAF story on he F-22: (I’m ex-Navy.. I’m using this as an example http://www.af.mil/news/story.asp?storyID=123022371)
During Exercise Northern Edge 2006 in Alaska in early June, the F-22 proved its mettle against as many as 40 “enemy aircraft” during simulated battles. The Raptor achieved a 108-to-zero kill ratio at that exercise. But the capabilities of the F-22 go beyond what it can do. It is also able to help other aircraft do better.