I came through this equation and would like to learn more about how to inteprete it. d is defined as actual value, and $\hat{d}$ is defined as predicted value.
Why does this equation (a) divides sum of least square error to the sum of $d_{i,j}^2$ ? (b) takes square root of (a) ?
May I know what's the name of this equation, that I can read further...
$ \sqrt{\frac{\sum_{i,j} (d_{i,j} - \hat{d}_{i,j})^2}{\sum_{i,j} d_{i,j}^2}} $