accuracy

A confusion matrix is the 2x2 of right and wrong predictions per class, and it is the reason a 99% accurate fraud model can be useless. The worked imbalance example, and how reading the matrix as precision and recall fixes the lie.

Say 'yes' and you've failed the integrity test; say 'no' flatly and you've failed the deal. The pass is a three-beat answer that turns the question into the reason to buy. Here's the script.