Lady, EVOLVED 
@Lady A document is just a thing that exists in recorded form, so as long as the statistic is recorded, sure. But it may also form part of a larger document, of which it would only make up, say, a fragment. (But that fragment, if removed, could be its own document!)
@Satsuma @Lady I guess I'm inclined to say that it must be fixed in some (any) medium? A picture is a document, a GIF is a document, and a movie is a document.
It would be hard to say that an informal conversation with no notes is a document. (So, arguably, a statistic therein like "I'm 60% inclined to have pizza for dinner." would not necessarily be a document? Hrm. It feels like it would be hard to endow it with the significance of a "statistic", but it's hard to say it isn't, either.)
@Satsuma @Lady Well, arguably no, DNA is its own recorded form. The apple seed probably contains many copies, but many of them will vary slightly. But certainly people have encoded data in DNA before, which seems like it would have to make that a document. Presumably that is also true of things that weren't intentional. (If a painting is a document, which I would argue it is, is a mounted leaf in a box a document? Sure. A tree? I guess I don't see why not; you could give it an accession number.)
you can get out of this one real easily with <doi:10.4242/BalisageVol5.Renear01>, if you¦re a coward