Wax LRS helps you measure the quality of the questions that are part of an assessment using statistical correlation, so you can identify bad questions more easily.
Correlation is between -1 and 1, and near-zero and negative correlations are bad. “Possibly zero” correlations are indicated in the interface of Wax in red by seeing if zero is within about two standard deviations of the measured correlation, though this is usually more an indicator of insufficient data than problematic questions for values much above zero.
Why does this work? It works because a near-zero correlation tells us that people who get a high score on the overall assessment are no more likely to get the question right than people who get a low score. A negative correlation tells us that people who score worse on the assessment are more likely to get the question right!