Quadratic loss function

A quadratic loss function is a way of measuring how wrong something is. It's used to measure the accuracy of a prediction. Imagine you have a dartboard. You throw a dart, and you want to measure how far off you were from the bullseye. You could measure that by drawing a line from the bullseye out to where the dart landed and measuring how long that line is. That line length would be the quadratic loss: the bigger the line, the bigger the mistake. In math, it looks like this: (actual - predicted)2. This can help you figure out how far off your predictions were so you can work to make them more accurate.