Notice that values for ρ range from -1 to 1, with +1 indicating perfect rank correlation, -1 perfect inverse correlation, and 0 no correlation.
note that this does not necessarily indicate a 'cheating' worker, for even if a worker is acting in good faith, they might not be able to perform the task adequately, due to misunderstanding the task, or neglecting to attempt to use a small number of edits.