### AUC – Area Under the Curve

The AUC is literally, the area under the curve. It measures the entire 2D space underneath the curve. If you’ve done any high school maths, you’ll recognise this as the integral of the curve.

The best model has an AUC of 1.

Sensitivity and Specificity are inversely proportional to each other.

When we increase our threshold that we’re happy with for false negatives, it allows us to increase our true positive rate.

We can understand this also when we look at the curve.

In the above example, we see a significant improvement when we move the threshold from 0% to 10% for false negative rate, as the true positive rate increases to 40%.

At a false negative rate of around 25%, the true positive rate is now 70%. We can use this to understand how well the model is performing.