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It can be hard, but if you know what to look for, you can get a pretty good idea of what's going on, you're very very lucky because I've done you a very professional diagram!
In the top histogram, see how the stack on the right-hand edge is near the bottom edge, and heading downwards, in JPEG you'd get a few bits of blown whites, but in RAW you're likely to be able to recover pretty much everything.
Whereas in the bottom example, the highlights have a lot of value right up to the very end of the graph, there's likely to be a lot of blown data in there that can't be recovered by RAW.
If this sounds patronising I apologise, but it's essentially how I read my histogram and I find it very effective, even my 6 year old 1Ds has a good 2 stops of highlight recovery, you have to get it pretty far out/shoot into the sun to lose image-destroying amounts of highlight.