As Trevor_Blake said, there's very little you can do apart from actually checking some of the data. An alternative is to ask or pay someone else or a group to verify it for you.
Of course, there's always the option of coding a probabilistic engine that mines for stats and gives you reliability estimates of certain claims using some bayes-fu. But that takes math, programming, and lots of work.
that takes math, programming, and lots of work
But sounds totally awesome. Especially if it can be created once and used over and over for different applications.
What I'm trying to figure out is, how to I determine whether a source I'm looking at is telling the truth? For an example, let's take this page from Metamed: http://www.metamed.com/vital-facts-and-statistics
At first glance, I see some obvious things I ought to consider. It often gives numbers for how many die in hospitals/year, but for my purposes I ought to interpret it in light of how many hospitals are in the US, as well as how many patients are in each hospital. I also notice that as they are trying to promote their site, they probably selected the data that would best serve that purpose.
So where do I go from here? Evaluating each source they reference seems like a waste of time. I do not think it would be wrong to trust that they are not actively lying to me. But how do I move from here to an accurate picture of general doctor competence?