It doesn't matter if bad testers exist. Presumably, the percentage of them is no...

		xboxnolifes 47 days ago \| parent \| context \| favorite \| on: Ford can't find mechanics for $120K: It takes math... It doesn't matter if bad testers exist. Presumably, the percentage of them is not increasing over time, so the drift can still be measured. And if they are increasing over time, then the drift is still measuring something.