"Informative" is the adjective form of "information". What's the adjective form of "data"/"datum"?
In Latin, datum is already an adjective of sorts, in so far as it is a form of the verb do (to give) and means 'that which is given'. If you had to make an adjective of it in English, you would have to use given, as in 'a given fact'.
How about statistical?
I realize it's not the same root word, but my dictionary1 shows a credible thread:
So long as the data is numerical or quantitative, at least, that word seems to work (although it might be more of a stretch if applied to, say, demographical data.)
1(Definitions from NOAD; emphasis added.)