You can filter out bad workers by preparing an additional well-labeled dataset and removing those who made even a single mistake in it. Also you can give the sa

You can filter out bad workers by preparing an additional well-labeled dataset and removing those who made even a single mistake in it. Also you can give the same task to several workers and check if they give the same label. However this won't protect against a bot using multiple accounts and giving answers based on a hash of a question so that the same question gets the same answer in every account.