[pmiller2]

They are if they're a representative sample. Margin of error is bounded by 1/sqrt(n) in that case.

[notafraudster]

That MOE would be extremely conservative given that the proportion of interest is far from p=0.5; the classical MOE would be +- 1.96 * sqrt(0.9 * 0.1 / 1200) = +- 1.697% -- but of course it's not a representative sample as you mention.