My lab partner and I (Inst. not HS) came up with the exact At. Wt. for a sample - which was in fact, a Magnesium salt. We didn't employ our memory of data from the Periodic Chart, etc. - we just weighed stuff accurately as we could manage. Sometimes the erors Do cancel-out.

(I recall the incident because the instructor Didn't smirk. I called that, Class..)

But yeah, all science is predicated upon working-backwards from an expected guesstimate. None of us integrates very well; differentiation is sooo much easier. Prolly the same with spawners of new 'theories' to justify What I *Know* is Right cha cha cha. (Doomed species - by the inescapable warz from that approach,) but W.T.F.