It's doesn't mean anything to just point at the source of an error though. You need to show that the error results in a bias (edit: or variance) on a large scal

It's doesn't mean anything to just point at the source of an error though. You need to show that the error results in a bias (edit: or variance) on a large scale. My point here was that it seems pretty plausible for the law of large numbers to take care of little variances like this, so if you want to claim their collection was problematic, explain which errors could occur consistently so as to reach a wrong conclusion.